1. In 1856, the Republican Party held its first convention in Wisconsin in response to the controversial Kansas-Nebraska Act. This act threatened to expand slavery into new territories, and the Republican Party was formed in opposition to it. The convention was held in a small schoolhouse in the town of Ripon, creating the first Republican Party in the nation.

2. In 1883, the Milwaukee Road Railroad was completed, connecting Wisconsin to the Pacific Northwest. The railroad was a major transportation route for goods and people, and its completion had a significant impact on the growth and development of Wisconsin's economy.

3. On May 21, 1917, Eugene V. Debs, a socialist labor leader and five-time presidential candidate, was sentenced to 10 years in prison for speaking out against the US government's involvement in World War I. Debs' conviction and imprisonment became a rallying point for the labor movement, and he was eventually released from prison after serving two and a half years.

4. In 1947, the University of Wisconsin-Madison announced the creation of the first nuclear reactor built on a university campus. The reactor, called the "Triga" reactor, was used for research and teaching and helped establish the university's reputation as a leader in nuclear sciences.

5. On May 21, 1972, John Wojtowicz and his accomplices attempted to rob a bank in Brooklyn, New York, in what became known as the "Dog Day Afternoon" robbery. Wojtowicz, a Wisconsin native, was the inspiration for the Al Pacino character in the movie of the same name. The botched robbery and ensuing 14-hour standoff with police became a media sensation and a cultural touchstone of the 1970s.