The Grant–Kohrs Ranch National Historic Site, created in 1972, commemorates the Western cattle industry from its 1850s inception through recent times.

[4] Grant started using the Deer Lodge Valley in 1857 to graze his cattle during the winter along the banks of the Clark Fork river near Cottonwood creek.

In August 1866, he sold his ranch to a cattle baron, Conrad Kohrs, for $19,200[5] and returned to Canada.

[6] Conrad Kohrs was born on August 5, 1835, in Wewelsfleth, in Holstein province, which was then a part of the German Confederation.

While the open range era was ending, Kohrs adapted successfully and was able to pay off the loan in only four years.

Kohrs and his half-brother, John Bielenberg, turned to more modern methods of ranching, including buying purebred breeding stock, fencing his rangeland and raising and storing fodder.

He bred what were called the "Big Circle" horses, reputed to be able to cover twenty miles of country in a half a day; a trait useful when gathering cattle spread over a very large area.

Ranchers using the open range for their herds lost upwards of 90% of their cattle to brutal cold and lack of feed.

Con Warren wanted to sell the Grant–Kohrs portion of his ranch to the National Park Service as a historic landmark.

[9] Throughout the 1970s, the National Park Service continued to acquire acreage from Conrad Warren, rehabilitate elements of the ranch and provide improvements for visitation to include a visitor center, interpretive trails and access for the public.

In 1974 the site became an independently operating unit of the National Park Service with its own superintendent, historian and budget.