1 was approved for funding by the Maryland General Assembly in 1972. In response to lobbying by Anne Arundel County residents, the MTA eliminated the south line from Phase 1 plans in 1975; the Baltimore Light RailLink was later built over much of the planned south line corridor.

When the Baltimore Metro Subway opened on November 21, 1983, only the "Northwest" line of the 1965 plan had come to fruition. This 12.2 km segment provided