Sarnia is located on the Saint Clair River and the southern end of Lake Huron, near Port Huron, Michigan (to which it is connected by bridge and railway tunnel). It is a busy port and one of Canada's principal centers for refining petroleum. Other manufactures include rubber, chemicals, motor-vehicle parts, and building materials. Agriculture is also an important part of the economy. The city’s economy diversified at the end of the 20th century, developing businesses related to tourism, health care, and software. A 2006 real estate survey has estimated the population of Sarnia, Ontario at 88,793.