1. Iowa became a state on December 28, 1846. However, on December 20, 1846, President James K. Polk had signed the Iowa Admission Act, which officially made Iowa a state the following week.

2. The deadliest tornado in Iowa's history occurred on December 20, 1871. The tornado, which traveled from southeast Missouri to northeast Iowa, killed 17 people and injured 50 more.

3. On December 20, 1924, the state of Iowa officially adopted the American Goldfinch as its state bird. The American Goldfinch, also known as the Eastern Goldfinch, is known for its bright yellow plumage.

4. In 1944, on December 20, the Iowa Supreme Court upheld the constitutionality of a law that required all Iowa school children to salute the American flag and recite the Pledge of Allegiance. The ruling was later overturned by the U.S. Supreme Court in 1943.

5. On December 20, 1968, the USS Iowa, the lead ship of its class and one of the most powerful battleships ever built, was launched at the Brooklyn Navy Yard in New York City. The ship was decommissioned in 1990 and is now a museum ship in Los Angeles, California.