1. In 1858, Wisconsin's first railroad, the Milwaukee and Mississippi Railroad, was completed, connecting Milwaukee and Waukesha. This helped to spur economic growth and development in the state.

2. On May 18, 1896, the U.S. Supreme Court upheld the constitutionality of the Wisconsin railroad commission's power to regulate railroad rates, a major victory for progressive reformers who sought to curb the power of big business.

3. In 1933, Wisconsin became the first state to establish a state income tax, which helped to fund New Deal programs aimed at stimulating the economy during the Great Depression.

4. On May 18, 1940, Wisconsin's legendary conservationist Aldo Leopold was awarded an honorary degree from the University of Wisconsin-Madison for his pioneering work in ecology and wildlife conservation.

5. In 1980, an F3 tornado struck the town of Colfax, Wisconsin, killing one person and injuring several others. The tornado was part of a larger outbreak of severe weather that swept across the upper Midwest that day.