Maryland began subsidizing the trains in 1974 and, in 1975, assumed full responsibility for the subsidy and equipment replacement.

Brunswick Line service was augmented in 1986 when Amtrak transferred its Washington–Martinsburg Blue Ridge to MARC after agreeing to subsidize the train for five years.

[6] Brunswick Line trains typically have four to six single- or bilevel passenger cars and one or two diesel locomotives.

Before they were replaced by new Bombardier Multilevel II cars, MARC's ex-Metra Pullman Gallery cars were used exclusively on the Brunswick Line, which is the only MARC line with all low-level platforms (except the Frederick Branch, which has a high-level platform at Monocacy station).

Connections to the Washington Metro's Red Line are available at Rockville, Silver Spring, and Union Station.