Although Southington was formally established as a town in 1779, its roots go back to a much earlier time. Samuel Woodruff, Southington's first white settler, moved from Farmington to the area then known as "Panthorne" that was settled in 1698. The settlement grew, prospered, and came to be known as "South Farmington" and then later, the shortened version, Southington.
The town's most important early visitor was General George Washington, who passed through the town in 1770 on his way to Wethersfield.
The Marion section of Southington is one of the most historic places in the town. It is the site of an encampment by the great French general, Jean-Baptiste Donatien de Vimeur, comte de Rochambeau, and his troops during the American Revolutionary War. In June 1781, the French troops under Rochambeau's command left Farmington and marched to their eighth camp through Connecticut, near Asa Barnes Tavern in the Marion section of Southington, now the Marion Historic District.
They camped there for four days. Rochambeau and his officers took shelter in the tavern, and the troops set up camp on a hill on the other side of the road. The area of the encampment has since become known as French Hill, and a marker on the east side of Marion Avenue commemorates the French campsite. According to Rev. Timlow's Sketches of Southington (1875), "Landlord Barnes gave a ball at his tavern, at which a large number of the young women of the vicinity were present; and they esteemed it something of an honor to have had a 'cotillion' with the polite foreigner." The celebrations-infused with spirits provided by Landlord Barnes-spanned the four nights they were in Southington. Rochambeau revisited Barnes's Tavern on the return march on October 27, 1782. According to Timlow, coins, buttons and other things were picked up in the vicinity many years after the two encampments. The Asa Barnes Tavern is now a private residence very near the camp site at 1089 Marion Avenue.
With the overall decline of industry in New England, and the construction of Interstate 84 in the mid 1960s, Southington developed into a bedroom community of which the town saw explosive growth and a population that has surged to over 42,000 today. 28% of the workers in Southington are still employed in manufacturing, most of them in the production of fabricated metals and aircraft.
In May 1942, during World War II, the town was selected by the War Department to be highlighted in a defense booklet called Southington, CT—Microcosm of America. Photographers roamed the community taking photos of residents at work, at play and in their homes and churches. The final publication was intended to show friends and foes alike in Europe the typical American citizens and families, their traditions and values. Thousands of copies were dropped from military airplanes over Europe during the Nazi German Occupation.
Each year, Southington is home to the Apple Harvest Festival, an effort to bring together local businesses and denizens from the area and surrounding cities. This has been a tradition of the town since 1969, generally spanning six weekdays and two weekends. Its highlights include a town parade, carnival rides and games, musical performances, and a wide selection of unique recipes and foods served by community cornerstones including the Boy Scouts of America, local churches, the Southington Fire Department and Police Department, the Southington Rotary Chapter, and the Southington Jaycees.
Two of Southington's main state roads are named for notable residents. Southington's portion of Route 10 is named the Louis G. Tolles Memorial Highway for the late state Grange leader and legislator (1885–1956). The road was dedicated on Aug. 6, 1960, and rededicated with new signs on Oct. 6, 2007. A section of Route 364 (Oakland Road and Berlin Street) was dedicated as the Officer Timothy Foley Memorial Highway on Sept. 11, 2009, in honor of the first (and to date the only) Southington police officer killed in the line of duty. He died six days after being struck by a vehicle on Dec. 30, 1937.
In January 2011, John Weichsel retired as town manager after 44 years. He was hired by the first Town Council when the council/manager form of government was established in town in 1966. His tenure as a town manager in the same community is one of the longest in the United States. Weichsel died in 2013.