| County Seat | Elk Point |
|---|---|
| Former County Name | Cole County |
| Time Zone | Central |
| Towns | Alcester, Big Springs, Beresford, Elk Point, Emmet, Jefferson, Junction City, Richland, and Spink |
|---|---|
| Parks | Union Grove State park |
Union County is located in the extreme southeastern corner of the state of South Dakota. Its southern border follows the Missouri River; and, its eastern border follows the Big Sioux River. The northern border is shared with Lincoln County; and, its western border is shared with Clay County. Brule Creek is the county's principle inland stream. The county contains equal proportions of rolling prairie lands and bottom lands.
The settlement of Union County by Europeans can be traced back to the French trappers, who settled near the mouth of the Big Sioux. However, the county's first American settler was Eli B. Wixson, who settled at the location of the town of Elk Point on July 22, 1859. He lived in a log cabin, which was opened for the Wixson Tavern. He later enlarged this to accommodate travelers; and, Wixson kept a small stock of groceries. He also built the county's first post office at Elk Point in 1860 and served as postmaster. In the fall of 1860, a group of Native Americans settled near Eli Wixson's home and engaged in trading with him. After some difficulty, a Sioux warrior shot and killed Wixson before the group left.
During 1860, W. W. Adams built a second accommodation house. It served travelers and teamsters who traveled along the old government road, which lead up the Missouri River.
In 1861, more settlers started to move to Elk Point, Civil Bend, and selected locations along the Sioux City road. Eight families from Dubuque, Iowa settled near the future location of the town of Jefferson. In 1862, a group of Minnesota families settled near Elk Point. These families assisted in the organization of Dakota Territory.
In the fall of 1861, the first election was held. Austin Cole was elected to the upper house in the legislature. J. McBride and Chris Maloney of Civil Bend were elected to the House of Representatives.
The new county was defined and admitted by legislative enactment. Austin Cole wanted the county to be named Cole County. McBride and Maloney were in favor as long as Cole helped them to locate the county seat near Joseph Chapillion's land near the mouth of the Big Sioux instead of at Elk Point. This was passed by Dakota Territory's first legislature.
During the 1864 session, the boundaries between Cole and Lincoln were redefined. The act of 1864 redefined the boundaries between Union and Lincoln Counties and transferred two tiers of townships from Lincoln County to the northern end of Union County. At this time, Cole County's was renamed Union as a result of the influences of a member of the legislature named Mr. Rich. He also managed to have a law passed, which relocated the county seat to his claim on the Big Sioux, which was named Richland. However, new members were elected to the legislature during the next election; and, they passed a law which moved the county seat to its permanent location in Elk Point.
As early as 1871, the country of Emmet township was settled by a colony of Irish and German people. Most of the people who settled in Emmet were from Galena, Illinois; and, a number of others came from Freeport, Illinois.