The Montreal municipal administration asked municipalities of the South Shore of the Saint Lawrence River which one would be interested in the Metro and Longueuil got the link. Line 4 (Yellow Line) would therefore pass under the river, from Berri-de-Montigny station, junction of Line 1 (Green Line) and Line 2 (Orange Line), to Longueuil. A stop was added in between to access the site of Expo 67, built on two islands of the Hochelaga Archipelago in the river. Saint Helen's Island, on which the station of the same name was built, was massively enlarged and consolidated with several nearby islands (including Ronde Island) using backfill excavated during the construction of the Metro. Notre Dame Island, adjacent, was created from scratch with the same material. Line 4 (Yellow Line) was completed on April 1, 1967, in time for the opening of the World's Fair.