New Bedford to Weymouth via Bridgewater and Abington .
In 1930, the section north of Bridgewater was part of MA 102. South of Bridgewater wasn’t shown on the map. By 1933, the route existed as it does now north of MA 140. It appears that 140 was moved slightly west between 1953 and 1956, and 18 was extended south to cover the old routing of 140 south of their junction.
Between 1967 and 1969, the 140 expressway was proposed to run south to meet I-195 just west of New Bedford. 18 took over the former routing of 140 through New Bedford. The 1970 state highway map shows a small section of divided highway in New Bedford south of 195 to Pearl St. AAA shows the divided section extending south to US 6 by 1975; the state shows it by 1979.