Here are five interesting historical events that happened on June 20 in Iowa:

1. In 1919, the 19th Amendment to the United States Constitution was passed by Congress. This amendment gave women the right to vote, and Iowa was one of the first states to ratify it.

2. On June 20, 1944, the Iowa State Penitentiary in Fort Madison was the site of a prison riot that resulted in the death of six inmates and one guard. The riot was sparked by overcrowded and unsanitary conditions in the prison.

3. In 1967, the Iowa Supreme Court ruled in favor of a group of African American students who had been denied admission to the University of Iowa's College of Dentistry because of their race. The landmark decision helped pave the way for greater educational opportunities for people of color in Iowa.

4. June 20, 1970, marked the first official Juneteenth celebration in Iowa. Juneteenth commemorates the end of slavery in the United States and has since become an important day of reflection and celebration for African Americans.

5. On this day in 1983, the Iowa Caucuses were held for the presidential election. The caucuses are the first major event in the presidential nomination process and are considered an important indicator of a candidate's popularity and electability.