Duncan Farm, Archaeological site and historic farm in Jersey County, United States

Duncan Farm is a Woodland-period archaeological site on a farmstead south of Illinois Route 100 near Grafton, Jersey County, Illinois. It holds two burial mounds, each roughly 200 feet (61 m) long and 100 feet (30 m) wide, together with a habitation site. Its stratified deposits let archaeologists date the artifacts found there.

Duncan Farm is a Woodland-period archaeological site with two burial mounds and a habitation area. It was part of the Hopewell exchange system in Illinois and served as the closest neighboring village site to the Golden Eagle regional transaction center. The site was added to the National Register of Historic Places on August 24, 1982.

The site lies within the Hopewell exchange system of Illinois, and archaeologists link its two large mounds to the Golden Eagle regional transaction center, the nearest major trade and social hub. The mounds measure roughly 200 by 100 feet each, and the site is the closest neighbouring village site to Golden Eagle.

The site lies on private farmland south of Illinois Route 100 near Grafton; the mounds and habitation area are not developed for public tours, so access requires the landowner's permission. The two mounds measure roughly 200 by 100 feet (61 by 30 m) each, and the ground is unexcavated farmland, so plan for uneven terrain and no facilities.

The two mounds at Duncan Farm measure roughly 200 by 100 feet each, and their size led archaeologists to propose the site as a local transaction center within the Golden Eagle site's region. The site's stratification lets artifacts be dated with unusual ease.