Then beyond the hill's crest I saw Kingsport outspread frostily in the gloaming; snowy Kingsport with its ancient vanes and steeples, ridgepoles and chimney-pots, wharves and small bridges, willow-trees and graveyards; endless labyrinths of steep, narrow, crooked streets, and dizzy church-crowned central peak that time durst not touch; ceaseless mazes of colonial houses piled and scattered at all angles and levels like a child's disordered blocks; antiquity hovering on grey wings over winter-whitened gables and gambrel roofs; fanlights and small-paned windows one by one gleaming out in the cold dusk to join Orion and the archaic stars. And against the rotting wharves the sea pounded; the secretive, immemorial sea out of which the people had come in the elder time.
Kingsport was founded in 1639 by Puritan colonists from southern England and the Channel Islands, and quickly became a seaport and ship building centre.
Four witches were hanged in 1692.
During the American War of Independence, the Royal Navy blockaded the town and the town’s seafarers responded by becoming privateers.
In the 19th century sea trade dwindled and fishing became Kingsport’s main industry. Kingsport’s economy continued to shrink into the 20th century and today Kingsport relies mainly on summer tourism for its income. Artists have also flocked to Kingsport and many have become dreamers due to close proximity of the Dreamlands to the town. 
The ancient witch-cult probably came with the original settlers from England. Although four witches were hung in the 17th century witch-cult activity has continued into the 20th century undisturbed . The extent of the corruption is unknown but is very much underground and never seen by the summertime visitors.
Kingsport in print
Kingsport is featured in the following stories by Lovecraft: "The Terrible Old Man", "The Festival", “The Dream-Quest of Unknown Kadath”, "The Silver Key", "The Strange High House in the Mist", “The Case of Charles Dexter Ward”, and "The Thing on the Doorstep".
Maps of Kingsport can be found in Chaosium's H.P. Lovecraft’s Kingsport.
Andy Logam also a map of Kingsport and Lovecraft’s other Massachusetts towns. These can be found here: www.andylogam.com/maps_main.html
Real Life Inspiration
H.P. Lovecraft was inspired to model Kingsport after Marblehead, Massachusetts, a town lying south of Salem which inspired Arkham. He didn’t actually visit Marblehead until he had created Kingsport though.