This plaza is located close to the Dover city limit and was built in 1969. It was anchored by a The Mart (Mammoth Mart). The 45,800 sq.ft. store closed in 1973. It was replaced by King's which closed in december 1982. In 1983, Ames replaced King's.  Market Basket opened in the mid-80's and Ben Franklin opened in 1988.

Ames closed in february 1990 because the store was too close to the newly opened one in Dover. That other store was located in a newly acquired Zayre location and was bigger and located in a busy area.  Back at the Tri-City plaza, the former Ames space was split into 4 smaller stores. Tjmaxx opened in 1992 using part of the former Ames. Two smaller tenants were added. Market Basket expanded in 1998. In 2012 Fashion Bug announced it would close all of its stores including the Somersworth location.  

In 2016, Staples moved to the former cinema to the left of Market Basket. A Dairy Queen has been proposed for the former coffee kiosk in the plaza's parking lot. It opened recently.