1. The first tornado warning was issued on August 21, 1955.
On that day, the United States Weather Bureau issued a tornado warning for the first time in history. The warning was a result of high pressure system in the Midwest, which made it possible for storms to develop and cause tornados in Oklahoma.

2. The first Native American to serve in the U.S. Congress was born on August 21, 1867.
Charles Curtis was born in Topeka, Kansas, but he grew up in Oklahoma. Curtis was a member of the Kaw Nation, and he was elected to the U.S. House of Representatives in 1892. He later served as a U.S. Senator from 1907 to 1913, and he was the Vice President of the United States from 1929 to 1933.

3. The state's first execution by lethal injection was carried out on August 21, 1990.
Charles Troy Coleman was executed for the murder of his stepfather in 1979. Oklahoma was the first state to use lethal injection as a method of execution, which has since become the most common method used in the United States.

4. The Great Solar Eclipse of 2017 was visible from Oklahoma on August 21, 2017.
On that day, a total solar eclipse was visible across a narrow band of the United States, including Oklahoma. During the event, the moon completely blocked the sun for a few minutes, creating a stunning natural spectacle that was viewed by millions of people.

5. The Oklahoma City bombing trial began on August 21, 1997.
The trial of Timothy McVeigh, who was responsible for the bombing of the Alfred P. Murrah Federal Building in Oklahoma City, began on August 21, 1997. McVeigh was eventually convicted and executed for his crimes, which killed 168 people and injured over 800 others. The bombing remains one of the deadliest terrorist attacks in U.S. history.