Jefferson County, commonly referred to as “Jeffco,” is named after former president Thomas Jefferson and covers 774 square miles in central Colorado west of Denver. Jeffco is bordered to the north by Boulder and Broomfield Counties, to the east by Adams, Denver, Arapahoe, and Douglas Counties, to the south and west by Park County, and to the west by Gilpin and Clear Creek Counties. Jeffco’s southeastern border follows the South Platte River out of Waterton Canyon.
With a population of 534,543 as of 2010, Jefferson County is the fourth populous county in Colorado. Golden, the county seat, sits at the mouth of Clear Creek Canyon and has a population of 18,867. Most Jeffco residents—some 280,000—live in the Denver suburbs of Arvada, Wheat Ridge, and Lakewood, which are separated by the county’s major highways. In northern Jefferson County, Interstate 70 divides Arvada to the north and Wheat Ridge to the south. Farther south, US Highway 6 divides Wheat Ridge and Lakewood. A conglomeration of suburban communities, including Columbine and Ken Caryl, lies across US Highway 285 south of Lakewood. The small community of Morrison (population 430) is nestled against the foothills just south of I-70 and the mountain suburb of Evergreen (population 9,038) is located off State Highway 74 west of Morrison.
Straddling mountains, cities, and plains, the county has a long and storied history that dates back to the Ute, Arapaho, and Cheyenne Indians and white prospectors of the Colorado Gold Rush. Jeffco is also home to several popular areas within the Denver Mountain Parks system, including Red Rocks Park and Amphitheatre, Genesee Park, and Lookout Mountain.
The Jefferson County area has a long history of human habitation, attracting groups of hunter-gatherers since prehistoric times. An archaeological site on Magic Mountain south of Golden reveals that Paleo-Indian people hunted and gathered in the area as early as 4,000 BC.
By the mid-sixteenth century, Ute Indians occupied the Front Range, hunting elk, mule deer, bison, and other game and gathering a wide assortment of berries and roots. In the summer they followed game into mountain parks, such as Jeffco’s Elk Meadow Park, while the present site of Golden was a favored winter camp. Utes lived in temporary dwellings such as tepees or wickiups. By the 1640s, the Utes had obtained horses from the Spanish, and some groups began venturing onto the plains to hunt buffalo.
By the early nineteenth century, Arapaho and Cheyenne peoples arrived in the Jeffco area. Unlike the Utes, who primarily lived in the mountains, and the Cheyenne, who mostly kept to the plains, the Arapaho ranged across both landscapes, following buffalo across the plains and warring with Utes for hunting ground in the high country. Like the Utes, the Arapaho and Cheyenne lived in wickiups or tepees and wintered in the area of present-day Denver and Golden.
Early American Era
The United States acquired present-day Jefferson County as part of the Louisiana Purchase in 1803. Official American exploration began with the arrival of Maj. Stephen H. Long’s expedition in 1820. Thereafter, white trappers and traders began filtering into the area, hunting beaver and other fur-bearing animals.
The late 1850s brought hundreds of gold seekers to Colorado’s Front Range. A significant discovery along Cherry Creek in 1858 by William Green Russell’s party is credited with setting off the Colorado Gold Rush of 1858–59. In spring 1859, Russell again found pay dirt along Clear Creek. On November 29, 1858, Arapahoe City was established as the first white settlement in Jefferson County. John H. Gregory, a miner from Arapahoe City, kept Colorado’s gold fever running high when he made a discovery near present-day Black Hawk in May 1859.
In June 1859, Golden City was established at the entrance of Clear Creek Canyon as a supply center for miners. In 1860 the surveyor Edward L. Berthoud arrived, and the next year he located Berthoud Pass and surveyed a wagon route from Golden City to Utah. Berthoud would become one of Golden’s most famous citizens, serving as speaker of the territorial legislature in 1866 and lending his name to the town of Berthoud in Weld County.
With the establishment of mining camps and Golden City, the area’s indigenous people now had to contend with more than just each other for resources. Miners killed game and cut timber to build homes and mining structures and Golden City and Denver now lay atop the Indians’ prime wintering grounds.
Seeing the Native Americans as a hindrance to white settlement and economic development, the US government sought to remove them. Some Arapaho and Cheyenne relocated to eastern Colorado after the Treaty of Fort Wise in 1861. In 1864 the Sand Creek Massacre in present-day Kiowa County provoked an all-out war between the United States and several Indian nations on the Colorado plains. In 1867 the Medicine Lodge Treaty created the Cheyenne-Arapaho Indian Reservation in present-day Oklahoma, and by 1869, most of Colorado’s Cheyenne and Arapaho had moved there. The Treaty of 1868, meanwhile, created the Consolidated Ute Indian Reservation on Colorado’s Western Slope.
By the fall of 1870, Golden and Denver were linked to the rest of the country by three separate rail lines, and the train whistles in Jefferson County signaled the end of one way of life and the beginning of another. The last documented Ute encampment, led by Colorow, was recorded in 1876.
Jefferson County was created with the establishment of the Colorado Territory in 1861, with Golden City as county seat. Although the economy was initially dependent on mining, farming and ranching also provided reliable income for the county’s first residents. Beginning in the late nineteenth century, Jefferson County developed first as a supplier of food and mountain resources to the larger metropolis of Denver and later as a resource-consuming metropolis itself.
As one of Colorado’s two largest cities at the time, Golden City sparred with Denver to become the capital of the new territory. Golden City claimed greater importance because it represented the interest of the territory’s mining communities while Denver saw itself as a broker and political headquarters for the whole territory. After serving as territorial capital from 1862–67, Golden City ceded the title to its rival on the plains.
The late nineteenth century was a period of rapid growth for Jefferson County. The county population grew from 2,390 in 1870 to 6,804 in 1880 and increased to 9,306 by the end of the century. By 1879, Golden, which had dropped the word City from its name in 1872, had grown into a prosperous city, albeit not without pitting itself against its rival, Denver. In the fight for the Colorado School of Mines during the late 1860s, Denver’s status as the state capital actually helped Golden’s case for hosting the college; the school was founded in Golden in 1874 to help train engineers and geologists for the mining industry. In 1873 German immigrant Adolph Coors and his partner Jacob Scheuler brought another major industry to Golden when they founded the Coors Brewery. Coors attained sole ownership in 1880. Today, the brewery remains one of the city’s major employers and tourist attractions.
In 1869 Arthur Lakes, a deacon of the Episcopal Church, came to Golden to preach in mining camps and teach drawing and geology at Jarvis Hall Collegiate School (later Colorado School of Mines). In 1877 Reverend Lakes was searching for plant fossils on the hogback formation above the town of Morrison (established in 1872) when he discovered a set of fossilized dinosaur bones. Lakes eventually sent samples of the fossils to the Peabody Museum of Natural History at Yale University, setting off a rush of paleontologists to Jefferson County. The hogback yielded so many bones it eventually became known as Dinosaur Ridge. Among the species discovered at Dinosaur Ridge were Apatosaurus and Colorado’s state fossil, Stegosaurus.
Jeffco’s rocks held more than gold and fossils. Coal mining began as early as 1859, and by 1880, there were ten coal mines in the county producing 45,000 tons per year. Though coal mining was essential to the state’s economic development, it proved to be extremely dangerous. In 1870, for example, a methane gas leak killed one of the owners of the Leyden Mine and in 1889 a flood at the White Ash Mine—on what is now the campus of Colorado School of Mines—killed ten workers.
Miners of gold and coal had to be fed, and ranchers around Evergreen, Coal Creek Canyon, Conifer, and Pleasant Park raised cattle and chickens to sell in Golden, Denver, and Central City. Farmer David Wall dug the county’s first irrigation ditch off Clear Creek in 1859, and by the end of the year, the county had two more ditches. The farms that became the basis for the town of Wheat Ridge were also established in 1859.
Arvada became one of the principal farming communities in early Jeffco. The town was founded in 1859 as Ralston Creek. It was originally named for Lewis Ralston, a member of the Cherokee party who made one of the first gold finds along the Front Range in 1850. In 1858 Ralston led a group of gold seekers back to the area, and when the surface gold was panned out, a number of miners took to farming. The fertile land between the creeks coming out of the mountains proved indispensable to feeding the mining communities.
Arvada’s farmers supplied Denver with wheat, corn, oats, plums, melons, cherries, and strawberries, as well as celery and other vegetables. W.A.H. Loveland’s Colorado Central Railroad arrived in 1870, allowing farmers to more easily export their crops. By the time of its incorporation in 1904, Arvada declared itself “Celery Capital of the World.” As a suburb of Denver, the city grew rapidly throughout the twentieth century.
Lakewood, another Denver suburb in Jeffco, was platted in the summer of 1889 by W.A.H. Loveland and Charles Wech. By 1891, electric trolleys connected Golden, Arvada, and Lakewood.
While its suburban population increased during the twentieth century, Jeffco increasingly sought to balance that development with the preservation of its many scenic natural areas. Genesee Park, for example, was established as Denver’s first mountain park in 1912 and, at 2,413 acres, is the largest in the system. In 1914 the park was the site of the reintroduction of buffalo and elk, two species that were hunted nearly to extinction in Colorado during the late nineteenth century.
Towering above the town of Morrison is a cluster of large red sandstone outcrops. The natural setting of the rocks, which are over 250 million years old, offers near-perfect acoustics. This drew the attention of entrepreneur John Brisben Walker in the early 1900s. Walker was the first to use the Red Rocks area as a music venue, putting on several concerts between 1906 and 1910. In 1927 the city of Denver bought the site from Walker, and with the help of the Civilian Conservation Corps and the Works Projects Administration, completed construction of the modern amphitheater by 1941. The venue has since hosted many famous musicians, from the Beatles to opera singers and reggae groups. It also hosts the Easter Sunrise Service, an annual nonsectarian outdoor service that began in 1947. Red Rocks Park was designated a National Historic Landmark on August 3, 2015.
In 1951 the US government set up a nuclear weapons facility on a floodplain between Boulder and Golden called Rocky Flats. The facility brought some 5,000 jobs to the Arvada community, but the large amount of radioactive waste it created posed a threat to workers and the environment. The top-secret facility often buried nuclear waste in the surrounding landscape and was prone to fires, the largest of which nearly ignited a regional catastrophe in 1969. From the time it opened until after a joint raid by the FBI and the US Environmental Protection Agency shuttered it in 1989, the Rocky Flats facility produced some 70,000 nuclear bomb cores. In 1991 the plant was decommissioned, and the government began cleaning up the surrounding area. Today, the Rocky Flats area is a wildlife refuge.
In 1955 the aerospace manufacturing company Glenn L. Martin established a complex in southern Jefferson County. The company was renamed Martin Marietta Corporation in 1961 after merging with American Marietta Corporation, a sand and gravel supplier. In 1995 it merged with the aerospace company Lockheed, forming Lockheed-Martin. Today, the Lockheed-Martin facility is the largest employer in Jefferson County with 4,875 employees.
As commercial and residential development expanded after World War II, Jeffco residents sought to put some of the county’s natural areas beyond the reach of bulldozers. In 1972 PLAN Jeffco and the League of Women Voters of Jefferson County proposed to the county commissioners a one-half of 1 percent sales tax increase that would support the preservation of natural areas within the county. Voters approved the tax, and Jeffco Open Space became the nation’s first county-level preservation program funded by a local sales tax.
Important as they were to making Jefferson County a decent, peaceful place to live, robust economic development and a commitment to natural places did not prevent a national tragedy from occurring there. On April 20, 1999, two students went on a grisly shooting spree at Columbine High School, killing twelve students, one teacher, and themselves. The shooting was a catalyst for increased security in public schools across the country, as well as national debates on gun control and investigations into bullying.
Today, Lockheed-Martin remains a major employer in Jeffco, along with the Coors Brewery in Golden, two medical centers, and Terumo BCT, a medical technology company. Each provides more than 2,000 jobs. The National Renewable Energy Laboratory in Golden adds another 1,720. Suburban development in Jefferson County has expanded in surrounding communities such as Evergreen, Indian Hills, and Conifer.
Although commercial businesses expand the county’s tax base and give residents the opportunity to live amid the scenic foothills, suburban development presents unique challenges, including management of natural areas and dealing with the threat of wildfire. In July 2015, for instance, the North Hogback Fire prompted the Jefferson County Sheriff’s Office to issue pre-evacuation orders for the suburban communities of Ken Caryl and North Ranch.
Since its foundation in 1972, Jeffco Open Space has acquired 53,000 acres of land for preservation and helped create more than 3,100 acres of conservation easements on private land. To maintain the integrity of its natural spaces amid a growing population, the organization continues to enforce a lengthy list of rules for fishing, wildlife interaction, fires, and other activities.
While most of Jefferson County today can be described as either suburban or urban, there are still more than 500 farms in the county producing melons, potatoes, and vegetable crops. The county’s cattle herd numbers about 2,000 and ranchers also raise about 2,800 horses and ponies.
Jeffco has also endeavored to honor its Native American past, particularly the life of the Ute leader Colorow. In 2013 the Jefferson County Historical Commission’s Landmark Designation Committee approved the Colorow Council Tree near Dinosaur Ridge as a county landmark. The tree, located on the historic Rooney Ranch, indicates where Colorow met with white settlers to broker peace. The landmark designation protects the tree and the area around it from removal or development. Additionally, in October 2015, the Jefferson County Historical Commission inducted Colorow into the Jefferson County Hall of Fame, and an exhibit about the Ute leader opened in Evergreen’s Hiwan Homestead Museum in 2016.