The city was merged on January 1, 2002 with the communities of Boucherville, Brossard, Greenfield Park, Le Moyne, Saint-Bruno-de-Montarville, Saint-Hubert, and Saint-Lambert. These cities have become boroughs of the new city. Saint-Lambert and Le Moyne became one borough, and the former city of Longueuil became the borough of Vieux-Longueuil. Locals refer to the borough of Vieux-Longueuil as "Longueuil proper" to distinguish it from the part of the borough known as "Old Longueuil".
In 1996, the population of the components of the current city of Longueuil totalled 373,012, making it the fourth largest city in Quebec. The current city has an area of 273.52 sq.km. Residents of Longueuil are called Longueuillois.
Most of the community's residents commute to Montreal to work. This generates major traffic problems; owing to the width of the Saint Lawrence River between the Island of Montreal and the south shore, there are only five automobile crossings (the Honoré-Mercier, Champlain, Victoria, and Jacques-Cartier bridges and the Louis-Hippolyte-Lafontaine tunnel), and they are severely congested.
The city is also served by the Longueuil metro station, connected to downtown by the yellow line of the metro. The Réseau de transport de Longueuil (RTL) bus lines almost all terminate either at Longueuil metro station or cross over the Champlain bridge to arrive at the Terminus Rive-Sud in downtown Montreal (under the 1000 de la Gauchetière office tower, Bonaventure metro). The Mont-Saint-Hilaire commuter train line also serves the south shore.
There are several explanations for the origin of the city's name. According to Abbé Faillon, Charles Le Moyne (1626-1685), lord of the area starting in 1657, named it after a village which is today the seat of a canton in the district of Dieppe in his homeland of Normandy.