Lake Ontario, the 14th largest lake in the world, is the smallest of the Great Lakes in surface area.
It ranks fourth among the Great Lakes in maximum depth, but its average depth is second only to Lake Superior.
Lake Ontario lies 325 ft (99 m) below Lake Erie, at the base of Niagara Falls.
The falls were always an obstacle to navigation into the upper lakes until the Trent-Severn Waterway, along with the Welland and Erie Canals were built to allow ships to pass around this bottleneck. The oldest lighthouse on the U.S. side of the Great Lakes was set up at Fort Niagara in 1818 to aid navigation.
The basin is largely rural, with many scenic resort areas.
A few large urban areas, including Ontario's capital city (Toronto), are located on the Canadian shoreline.
In 1972-73, 1,000 scientists, engineers and technicians undertook the most extensive survey ever made of a Great Lake.
References: Lake Ontario brochure, 1990, Michigan Sea Grant
WATER SURFACE AREA: 7,340 sq. miles / 18,960 sq. km.
TOTAL DRAINAGE BASIN AREA: 24,720 sq. miles / 64,030 sq. km. DRAINAGE BASIN AREA BY STATE/PROVINCE:
New York: 13,500 sq mi; 35,000 sq km Ontario: 11,200 sq mi; 29,100 sq km Pennsylvania: 100 sq mi; 300 sq km
SHORELINE LENGTH (including islands): 712 miles / 1,146 km.
ELEVATION: 243 ft. / 74 m.
OUTLET: St. Lawrence River to the Atlantic Ocean
RETENTION/REPLACEMENT TIME: 6 years
NAME: Champlain first called it Lake St. Louis in 1632. On a Sanson map in 1656, it remained Lac de St. Louis. In 1660, Creuxius gave it the name Lacus Ontarius. Ontara in Iroquois means "lake," and Ontario, "beautiful lake."
References: Great Lakes Atlas, Environment Canada and U.S. Environmental Protection Agency, 1995