The rich farm country of southeast South Dakota lies in the triangle formed by the Missouri River to the west and the Big Sioux River to the east as they flow toward their confluence about 37 miles southeast of this point, and this land drew settlers to Dakota Territory. What may have been the number one entry in the entire United States under the Homestead Act was filed near here when, just minutes after midnight on Jan. 1, 1863, Vermillion printer Mahlon Core filed his claim for 159 1/2 acres on a site about seven miles due east of here and some three and one-half miles north of present-day S.D. Highway 50, though he never proved up his claim and it lapsed. Most early settlement in South Dakota occurred in this southeast corner of the state, where Sioux Falls, the state's largest city, was settled in 1857, Vermillion was established in 1859, and Yankton in 1858. Highway 50 forms a corridor in time to the territorial days of South Dakota, and Union, Clay, and Yankton Counties along this highway were among the earliest organized in Dakota Territory in 1862. Their names reflected the times: Union County, originally called Cole, was renamed in 1864 because of northern sentiment during the Civil War; Clay County was named for Senator Henry Clay; and Yankton County took its name from the Sioux tribe that gave up that area in an 1859 land cession. Yankton, 33 miles west along the Missouri River, was a major steamboat port in Dakota Territory, a status that helped make it the capital of Dakota from 1861-1883, and it was often called the Mother City of the Dakotas. Education was also a key interest of early legislators, and Vermillion, eight miles west on Highway 50, reflects that in the University of South Dakota: Vermillion was designated as the site for the territorial university in 1862, and although the institution, then called the University of Dakota, did not begin classes until 1882 with 35 students, Vermillion became the home of the University of South Dakota when statehood came in 1889.