1. On May 18, 1870, the first African American senator of the United States, Hiram Rhodes Revels, addressed the Maryland legislature alongside another African American senator, Blanche K. Bruce, in an effort to persuade lawmakers to support the Civil Rights Act of 1870. This act sought to protect the rights of African Americans in a post-Civil War America.

2. In 1895, Baltimore native and accomplished violinist, Joseph Douglass Jr., debuted at Carnegie Hall in New York City on May 18. Douglass was the grandson of famed abolitionist Frederick Douglass and was known for his unique blend of classical and African American musical styles.

3. On May 18, 1927, the first Boeing 40A planes arrived at Baltimore's Glenn L. Martin Airport. These planes were the first commercial airplanes to operate between Baltimore and Washington D.C.

4. In 1950, the Maryland state flag was officially adopted on May 18. The flag features the coats of arms of the Calvert and Crossland families, who founded the state. The flag is unique in its design, utilizing the heraldic colors of red, white, black, and gold.

5. On May 18, 1973, legendary baseball player and Baltimore Orioles third baseman Brooks Robinson hit his 250th career home run. Robinson was known for his defensive prowess and was inducted into the Baseball Hall of Fame in 1983.