Fort Ridgely was a frontier United States Army outpost from 1851 to 1867, built 1853–1854 in Minnesota Territory. The Sioux called it Esa Tonka. It was located overlooking the Minnesota River southwest of Fairfax, Minnesota. Half of the fort's land was part of the south reservation in the Minnesota river valley for the Mdewakanton and Wahpekute tribes. Fort Ridgely had no defensive wall, palisade, or guard towers. The Army referred to the fort as the "New Post on the Upper Minnesota" until it was named for two Maryland Army Officers named Ridgely, who died during the Mexican–American War.

Fort Ripley was a United States Army outpost on the upper Mississippi River, in mid-central Minnesota from 1848 to 1877. It was situated a few miles from the Indian agencies for the Ho-Chunk and Ojibwe in Iowa Territory and then the Minnesota Territory. Its presence spurred immigration into the area and the pioneer settlement of Crow Wing developed approximately 6.75 miles (10.86 km) north of the fort. The post was initially named Fort Marcy. It then was renamed Fort Gaines and in 1850 was renamed again for distinguished Brigadier General Eleazer Wheelock Ripley of the War of 1812. It was the second major military reservation established in what would become Minnesota.