In the 1920s, State Highway 108 followed New State Road and Tolland Turnpike from US 6 to Route 83 in Manchester; then today's Route 83 northerly to Massachusetts.

The Nichols Avenue part of the modern Route 108 was Trumbull's first highway, then called the Farm Highway, which opened in 1696.

The modern Route 108 was commissioned on Jan. 1, 1932. It didn't get a lot of respect in the early years. The original route was from a dead-end in Huntington village to the corner of Perry and White streets in Shelton, for a length of 3.45 miles. It appears that the state-maintained part of Route 108 did not connect with any other signed route.

On May 1, 1951, a state senate bill was introduced to add all of Route 108, from Shelton to Penny Ave. in Trumbull (Route 65 at the time). Maps (but not the ConnDOT spreadsheet) show an extension south in 1952.

In 1957, however, it was omitted from the state map, and didn't reappear until 1960. This might have merely reflected a mix of state and local responsibility for the route.

Route 108 has fared better since then. In 1963, Route 108 was given 3 more miles (Nichols Avenue, from Route 8 to US 1) formerly part of Route 113. Now, both routes 8 and 15 explicitly denote exits to Route 108, ignored no longer.

In 1999, Route 108 was rerouted slightly in Shelton. Instead of following Perry Avenue and White Street to end at Route 110, it now follows Wooster St and Coram Avenue to its end, picking up another 0.11 mile in length.

In 2003, The Shelton Economic Development Corporation, in a section of its website titled "Look to the Future", stated an intention to improve the traffic pattern of Route 108 through Shelton Center. Details are not yet provided.