The Huntington Avenue subway opened in 1941, cutting travel times through congested Copley Square. Ownership passed from the Boston Elevated Railway to the Metropolitan Transit Authority in 1947, and to the MBTA in 1964. Tremont Street subway service was designated as the Green Line in 1965, with the Huntington Avenue line becoming the E branch in 1967. Service was modified numerous times during the early MBTA era, including a major reconstruction of the line in 1980–82. In 1985, service past Brigham Circle was replaced with the route 39 bus – a "temporary" change that controversially became permanent, although service as far as Heath Street was restored in 1989 after replacement of the street trackage on Huntington Ave. The downtown terminal of the E branch underwent a number of changes during the MBTA era; from 1987 to 2020, it was usually . In May 2020, the E branch was cut back to North Station for construction of the Green Line Extension, as part of which it will be extended to in 2021.