1. On April 18, 1848, the Wisconsin territorial legislature passed an act establishing the University of Wisconsin-Madison. It was originally named "University of the Territory of Wisconsin" and its first building, North Hall, was constructed in 1851. Today, the University of Wisconsin-Madison is a prominent public research university and one of the oldest and largest in the United States.

2. The deadliest tornado in Wisconsin history occurred on April 18, 1880. The tornado touched down in the town of Waupaca and traveled southeast for 62 miles, killing at least 25 people and injuring many more. The tornado was estimated to be an F4 on the Fujita scale, with winds up to 250 mph.

3. On April 18, 1942, the Doolittle Raid took place during World War II. Led by Lieutenant Colonel James Doolittle, the raid was the first retaliation by the United States against Japan after the surprise attack on Pearl Harbor. The raid involved 16 B-25B Mitchell bombers taking off from the USS Hornet and bombing targets in Tokyo and other cities in Japan. Although the raid caused minimal damage, it boosted American morale and forced Japan to divert resources for home defense.

4. On April 18, 1983, the Wisconsin Badgers won their first NCAA men's ice hockey championship. The Badgers defeated the Harvard Crimson 6-2 in the championship game in Grand Forks, North Dakota. The team was led by Hobey Baker Award winner Mark Johnson, who would later become a successful coach for the Badgers women's hockey team.

5. In 2013, on April 18, the Wisconsin Department of Natural Resources reported that Wisconsin had reached its highest number of active bald eagle nests in 13 years, with 1,338 nests recorded. Bald eagles were once endangered due to hunting and the use of pesticides, but a ban on DDT and other conservation efforts have helped the population recover. Wisconsin is now home to one of the largest bald eagle populations in the lower 48 states.