New Haven was founded in 1637-38 by Puritans led by Theophilus Eaton and John Davenport. It was one of the first planned communities in America and was the chief town of a colony that later included Milford, Guilford, Stamford, Branford, and Southold (on Long Island). Its government was theocratic; religion was a test for citizenship, and life was regulated by strict rules (see blue laws). In 1665 the colony was reluctantly united with Connecticut; it was joint capital with Hartford from 1701 to 1875.

In the late 18th and early 19th cent., New Haven was a thriving port. Manufacturing grew, and New Haven firearms, hardware, coaches, and carriages became famous products. New Haven was raided by a British and Tory force in the American Revolution, and the port was blockaded during the War of 1812. The world's first commercial telephone exchange was established there in 1879.

Since the 1950s, New Haven has received national attention for its pioneering urban renewal projects. The nation's first antipoverty program began there in 1962. Despite these improvements, the city suffered a serious race riot in 1967. New Haven's manufacturing-based economy has since declined, and by 1990 manufacturing employed less than 20% of city's workforce.

The city centers upon a large public green, dating from 1680, on which stand three churches built between 1812 and 1816—Center and United churches (both Congregational) and Trinity Church (Episcopal). Many old buildings have been preserved, and there is a historic district. Landmarks in the city are two traprock cliffs—West Rock, with the Judges' Cave, and East Rock. Noah Webster and Eli Whitney lived and are buried in the city.