They became home to sprawling country estates belonging to Philadelphia's wealthiest families, and over the decades became a bastion of "old money".

The Main Line region was long part of Lenapehoking, the homeland of the matrilineal Lenape Native Americans (the "true people", or "Delaware Indians").

[5] However, what might be termed the "Celtification" of many Main Line place and street names occurred long after colonial times.

Part of the national trend of suburbanization, this drove rapid investment, prosperity, and growth that turned the area into greater Philadelphia's most affluent and fashionable region.

Estates with sweeping lawns and towering maples, the débutante balls and the Merion Cricket Club, which drew crowds of 25,000 spectators to its matches in the early 1900s, were the setting for the 1940 Grant/Hepburn/Stewart motion picture The Philadelphia Story.

Suburban service now extends west of the Main Line to the communities of Exton, Whitford, Downingtown, and Thorndale.

Another dimension of this story is illustrated by the community of Mount Pleasant, in Tredyffrin Township just north of Wayne.

Today, the Main Line is another name for the western suburbs of Philadelphia along Lancaster Avenue (U.S. Route 30) and the former main line of the Pennsylvania Railroad and extending from the city limits to, traditionally, Bryn Mawr and ultimately Paoli,[12] an area of about 200 square miles (520 km2).

Neighborhoods along the Main Line include nineteenth and early twentieth-century railroad suburbs and post-war subdivisions, as well as a few surviving buildings from before the suburban development era.

[13] The original Main Line towns are widely considered to follow the acronym "Old Maids Never Wed And Have Babies.

As early as 1887, Bala and Cynwyd were also included in atlases of the Pennsylvania Railroad[15] in Lower Merion Township and Montgomery County.

Other highways serving the area are the Schuylkill Expressway (I-76) which connects it to Philadelphia, and the Blue Route (I-476) which runs north to south connecting the region with the Northeast Extension and the Pennsylvania Turnpike to the north, and to Philadelphia International Airport and I-95 to the south.

Along the northern edge of the Main Line, US 202 runs from the Schuylkill Expressway in a southwesterly direction, crossing US 30 in Frazer.