[1] The region was historically occupied by the Sto:lo, a Halkomelem-speaking people of the Coast Salish linguistic and cultural grouping.

The term has historically been in popular usage for over a century to describe a region that extends from Horseshoe Bay south to the Canada–United States border and east to Hope at the eastern end of the Fraser Valley.

This definition makes the term Lower Mainland almost synonymous with the regional districts of Metro Vancouver and Fraser Valley.

[5] The region is bounded to the north by the Pacific Ranges and to the southeast by the Cascade Mountains, and is traversed from east to west by the Fraser River.

Less than ten percent falls as snow at sea level but the amount of snowfall increases significantly with elevation.

Regional districts were first created across British Columbia from 1966 to 1967 to form bodies for inter-municipal coordination and to extend municipal-level powers to areas outside existing municipalities.

Other peoples who historically occupied the region are the Sto:lo, Chehalis, Katzie, Kwantlen, Tsawwassen, and Semiahmoo; many of their territories overlap with those of the Musqueam, and with each other.

Many other peoples of the Georgia Strait region also frequented the lower Fraser, including those from Vancouver Island and what is now Whatcom County, Washington.

Higher than normal snow packs in the British Columbia Interior prompted municipal governments to start taking emergency measures in the region.

In 2007, the Lower Mainland was largely spared, although northern regions of the province, along the Skeena and Nechako Rivers, experienced floods.

[30] While earthquakes are common in British Columbia and adjacent coastal waters, most are minor in energy release or are sufficiently remote to have little effect on populated areas.

Volcanoes in this zone are capable of producing large quantities of volcanic ash that may cause short and long term water supply problems for Lower Mainland communities.