Southport is located along Long Island Sound between the Mill River and Sasco Brook (the Westport town line). The historic significance of Southport is because of its churches, harbor, homesteads of some of the first families in southwestern Connecticut and public buildings. It was settled in 1639, the downtown area has been designated a local historic district since 1967 and in 1971was listed as the Southport Historic District on the National Register of Historic Places.

In Southport's history the earliest recorded event was The Great Swamp Fight of 1637, in which English colonial forces led by Roger Ludlow and John Mason vanquished a band of about 100 Pequot Indians who had earlier fled from their home territory in the Mystic area and had taken refuge with about 200 Sasqua Indians who inhabited the area that is now Fairfield. The battle’s exact location is known to have been in the vicinity of Southport.

Mill River village, a part of Fairfield, was a small hamlet of a few houses and a wharf at the mouth of Fairfield's Mill River in the eighteenth century. Farm products were shipped from Mill River's small harbor to ports in New York and elsewhere.

Around 1831 the village had changed its name to Southport and was bustling with schools, stores, warehouses, elegant houses and churches. Southport had its own local government within the town of Fairfield before 1853. Southport became a leading coastal port on Long Island Sound carrying produce and goods to New York City. However, competition from steamboats and the railroad took its toll on prosperity. Resourceful shippers teamed with local farmers and businessmen to keep the port going and profitable until the end of the century.

First established in 1967, today, much of the old village area is part of a town historic district, where buildings from three centuries are protected for the future. The boundaries of the town historic district are the railroad; the Mill River and Southport Harbor; Church Street; and Old South Road and Rose Hill Road. Strict historic zoning regulations are in effect in the district. Listed on the National Register of Historic Places is The Southport Historic District.

Southport’s public library is the Pequot Library which is housed in a Romanesque building that was designed by Robert Robertson. It was built in 1887 and is a contributing property to the National Register Southport Historic District. The library is has a large collection of old and rare books. Its annual summer book sale featured more than 140,000 books for sale in the year 2007.

Southport’s ZIP code is 06890, and its scope extends north from the historic village area to include the Mill Hill area.

Southport has a private day school for children with learning disabilities called the Eagle Hill School. Since 1985 it has been located in the former Pequot School in Southport. The Southport Conservancy acquired the school building earlier to save it from demolition.

Southport is also served by the Fairfield Public Schools. Mill Hill Elementary School is located in Southport although children in some areas considered part of Southport but outside the census tract attend Timothy Dwight Elementary School. Both Mill Hill and Dwight Schools. These schools feed the Tomlinson Middle School and Fairfield Ludlowe High School.

The following notable people have lived in Southport:

Jason Robards, actor, producer and director Anatole Broyard, author James Truslow Adams, historian and writer John Akers, former chief executive officer of IBM Samuel J. Palmisano, chief executive officer of IBM

The Southport Fire Department was organized in 1895 as a volunteer fire department after a large arson fire in the village. Southport is also protected by Fairfield Fire Department's Engine 4, out of the Southport Firehouse.