The Kaplan-Hoover Bison Kill Site west of Windsor preserves one of the largest single-event Archaic arroyo kills ever found. Discovered in 1997 during construction of a housing development, the site was excavated by a Colorado State University (CSU) team led by Lawrence C. Todd. Because of the site’s proximity to Fort Collins and CSU, it was used for many field schools and teaching classes as well as tours and workshops designed to expose the public to archaeological research.

The Kaplan-Hoover Site is located in an old arroyo near the Cache la Poudre River. It was found in 1997 when construction and landscaping work at a nearby housing development removed more than ten feet of soil, revealing a bed of bison bones. Construction and landscaping continued—the site was even reseeded—but eventually the Department of Anthropology at CSU found out about the bones and started excavations in May 1998. Excavations continued into the early 2000s, with much of the work done by CSU’s summer field school.

The site’s main feature is the extensive bone bed, which measures about fifteen feet wide and at least three feet deep. Excavations revealed more than 4,000 identifiable bison bones from about 200 individual bison. Tooth wear indicates that the bison died in early fall, probably in a single large kill. The Native Americans responsible for the kill probably drove the bison either into or over the edge of an arroyo with steep banks, where the animals were trapped and slaughtered. The kill has been dated to approximately 835 BCE, which places it in the Late Archaic period (1250 BCE–100 CE), though it contains six or seven times as many animals as most other Late Archaic kills.

The bison bones at the site are mostly in excellent condition, indicating that they were buried soon after the animals died. In contrast to other bison kill sites, such as the much older Jones-Miller and Olsen-Chubbuck kills, the Kaplan-Hoover Site shows limited evidence of butchering. Few marrow bones were fractured or removed, and marks on the bones indicate light butchery focused on high-yield cuts of meat. This style of butchery is rare in a northern plains site and is more commonly found in kills on the southern plains, where food was more plentiful throughout the winter. It is possible that the timing of the kill in early fall, when temperatures would have been warm, meant that the carcasses had to be processed quickly before they spoiled. As a result of the light butchery, the bones show more carnivore damage than any other plains bison kill site.

The excavations helped excite the public about archaeological research. Many students at CSU did research or attended lectures there, and several thousand elementary, middle, and high school students received tours of the site and laboratory. In May 2000 an open house organized by the Colorado Archaeological Society attracted nearly 1,500 visitors.

After excavations were completed in the early 2000s, the site was backfilled and stabilized. In 2003 it was listed on the National Register of Historic Places.