Seneca Valley High School, located at 19401 Crystal Rock Dr. in Germantown, MD, is the largest public high school in the state of Maryland. The school first opened its doors in 1974 in its original building. It was constructed on land that formerly belonged to renowned baseball player Walter Johnson, who purchased it in 1935 and resided there with his family until his passing in 1946. Before the opening of Northwest High School in 1998, Seneca Valley was Germantown’s only high school. By 2025, Seneca Valley ranked 16th among the largest high schools in Maryland by enrollment.