The northern portion of the present Route 27 is nearly identical to the No. 25 streetcar line that operated during Baltimore's streetcar era. The Hampden line in Baltimore was the first electric streetcar that operated in the United States.
The northern part of present Route 27 closely follows the path of the No. 25 streetcar line from Baltimore's streetcar days. The Hampden line was the inaugural electric streetcar service in the United States.