Minnesota is the first state to offer troops at the outbreak of the Civil War. Governor Alexander Ramsey is in Washington, DC, when word of the attack on Fort Sumter arrives. He meets with Simon Cameron, the secretary of war, and offers one thousand Minnesota soldiers for the country's defense. He then telegraphs Lieutenant Governor Ignatius Donnelly, who summons volunteers from across the state.

The first regulated trout season opens.

The schoolchildren of St. Paul select the city's official flower, the sweet pea, in an election sponsored by the city's women's clubs. Other choices included the coreopsis, marigold, petunia, and aster. News of their choice is overshadowed by reports of the Titanic's sinking.

Jacob Wetterling, an eleven year old from St. Joseph, is kidnapped while riding his bike. His parents launch a search for him, and Jacob's photograph appears on posters from coast to coast. In 1990, Jerry and Patty Wetterling established a nonprofit foundation to focus national attention on missing children and their families. Twenty-seven years after the kidnapping, in September 2016, Daniel James Heinrich of Annandale confessed to abducting, sexually assaulting, and murdering Wetterling.

"General" James Dickson and a group of filibusters arrive at Fond du Lac. They plan to form an army of Métis people in the Red River area, march to California and capture it from Mexico, and establish a kingdom ruled by Dickson. The group travels as far as Pembina before being broken up by employees of the Hudson's Bay Company.

The Minnesota North Stars professional hockey team plays its first home game, beating the California Seals 3-1.

The US War Department orders Edward Janes, Wisconsin territorial marshal, to expel the Selkirk squatters from Fort Snelling military reservation. The fort's commander had complained of the settlers selling whiskey to the soldiers.

In the first such case in the United States, the Minnesota Supreme Court rules that the state's prohibition of same-sex marriages is constitutional. The case involves two men, Richard J. Baker and James M. McConnell, who had requested a marriage license from the Hennepin County clerk of court. When the clerk denied them the license, Baker and McConnell sued, eventually taking the case to the state's highest court.

Concordia College opens in Moorhead with a class of twelve students. At first a high school, Concordia would begin to offer college-level courses in 1907.

James Thompson, St. Paul's first African American resident, dies in Nebraska. Thompson had the distinction of being the only enslaved person sold in Minnesota. He was brought to Fort Snelling as the servant of an army officer in 1827, where he proved himself gifted in languages, quickly learning Dakota.