In the 1920s, State Highway 154 followed today's Route 47; around 1930, it annexed Charcoal Avenue, White Deer Rock Road, and part of Middle Road Tpke, connecting Middlebury Center to Woodbury.
At the same time, most of Route 154 was part of New England route NE-10, an ancestor of today's Route 10.
The modern Route 154 was commissioned in 1932, and originally was a small loop south of US 1 in Old Saybrook only, for a length of 6.06 miles. Going clockwise, Route 154 appears to have visited Saybrook Point and Fernwood as now, but then followed Maple Avenue back toward downtown. By 1935 it followed today's route back north, using Old Hammock Road, to end at US 1. The Maple Avenue section became Route 154A.
On Jan. 2, 1967, shortly after the Route 9 freeway opened in Old Saybrook and Essex, Route 154 was extended northward along Middlesex Turnpike (former Route 9) to Essex Road. (There is a very old section of former Route 9 -- Old Middlesex Turnpike and N. Main St., bisected by the railroad -- that was bypassed in the 1930s.)
In Nov. 1984, state Sen. Richard Schneller of Essex introduced a bill to rename Route 9A as Route 154. His reasoning: it would create a simpler, additional route between Old Saybrook and Middletown.
On June 1, 1986, the state made this change. Route 154 was extended further along Middlesex Turnpike to Route 153 at Ivoryton, then absorbed all of Route 9A to Route 9 exit 10 in Middletown.
The name change was unpopular to many residents; see the Route 9A page for details.
In 1995, the Main Street section in Old Saybrook was rehabilitated. The crumbled 30-year-old median was replaced with a 6-foot-wide brick median with granite curbing. Twenty-two planters, each with a gas street light, were installed along in the median.