Baltimore was a city in the state of Maryland, in the United States of America on Earth.
In 1914, Babe Ruth played for the professional baseball team in Baltimore, the Baltimore Orioles. (ST novel: Articles of the Federation)
The Great Starship Race run in 2269 started in Baltimore. The New Pride of Baltimore, the winning vessel in that competition, was named after the city. (TOS novel: The Great Starship Race)
Doctor Mark Piper was conducting research work at Johns Hopkins University in Baltimore in the early 2270s. (TOS novel: Traitor Winds)