The Blue Line is a rapid transit line of the Washington Metro system, consisting of 28 stations in Fairfax County, Alexandria and Arlington, Virginia; Washington, D.C.; and Prince George's County, Maryland, United States. The Blue Line runs from Franconia–Springfield to Downtown Largo. The line shares track with the Orange Line for 13 stations, the Silver Line for 18, and the Yellow Line for 7. Only 3 stations are exclusive to the Blue Line.

Prince George's County is located in the U.S. state of Maryland bordering the eastern portion of Washington, D.C. As of the 2020 U.S. census, the population was 967,201, making it the second-most populous county in Maryland, behind neighboring Montgomery County. The 2020 census counted an increase of nearly 104,000 in the previous ten years. Its county seat is Upper Marlboro. It is the largest and the second most affluent African American-majority county in the United States, with five of its communities identified in a 2015 top ten list.