Long before the cavalry post existed, the Mandan established On-A-Slant Village in the late 16th century at the confluence of the Missouri and Heart Rivers. Unlike most Plains tribes, the Mandan lived in permanent communities, building roughly 86 earth lodges that housed an estimated 1,000 to 1,500 people. The village was an economic hub where nomadic tribes came to exchange animal skins for agricultural products. A defensive ditch and palisade encircled the settlement, protecting its wealth. For two centuries the village thrived, until a devastating smallpox epidemic in 1781 killed the majority of inhabitants. The survivors moved north to join the Hidatsa along the Knife River. Among the notable figures born here was Sheheke, a Mandan chief who would later accompany Lewis and Clark back to Washington, D.C. in 1806. The artist-documented chief Mato-tope, painted by both George Catlin and Karl Bodmer, also grew up at this site.

The military arrived in June 1872, establishing an infantry post originally called Fort McKeen. By November of that year it was renamed Fort Abraham Lincoln and expanded with a cavalry post accommodating six companies. Among its 78 permanent wooden structures were barracks, officer's quarters, cavalry stables, a hospital, and a telegraph office. Water was hauled from the Missouri in wagons. The fort's primary mission was protecting crews building the Northern Pacific Railway. Custer and his wife Libbie arrived in 1873, making this their home. Their first house burned down in February 1874 and was rebuilt. For three years, Fort Lincoln was one of the most important military posts on the northern frontier, a staging ground for expeditions into contested Sioux territory that would culminate in the Great Sioux War of 1876.

When Custer led the 7th Cavalry out of Fort Lincoln in the spring of 1876, the objective was to force non-treaty Lakota and Cheyenne bands back to their reservations. The campaign ended at the Battle of the Little Bighorn on June 25, where Custer and over 260 of his soldiers were killed. The news reached the fort's remaining families and garrison with devastating effect. Without its most famous commander, Fort Lincoln continued to operate but gradually declined in strategic importance as the Northern Pacific Railway reached Montana in 1883. The Army formally abandoned the post in 1891. Within a year, local residents had stripped the fort for its nails and lumber, and the once-busy garrison crumbled into the prairie.

In 1907, President Theodore Roosevelt signed the deed transferring the fort's land to the state of North Dakota, creating Fort Abraham Lincoln State Park. Today the Custer House and seven other major fort buildings have been reconstructed, including barracks, the makeshift theater where soldiers once staged performances, and a stable. Guides dressed as 1870s laundresses and soldiers lead tours every half hour, and during summer months melodramas originally performed at the fort in the 1870s are revived in the rebuilt granary. Six earth lodges at On-A-Slant Village have also been reconstructed, where interpreters introduce visitors to Mandan culture and the village's two centuries of history. The park offers 95 campsites, horseback tours, hiking trails, and fishing along the Missouri, making it a place where military history, indigenous heritage, and prairie recreation converge.