7.85 miles; from Route 195 in Mansfield to I-84 in Willington.

In the 1920s, state highway 320 followed today's Route 177, between Route 4 and US 44.

The modern Route 320 was commissioned in 1963 along Ruby Road and Willington Hill Road, both town roads. My guess is the state adopted the route to provide a connector from I-84 to Storrs, in the same way Route 229 was a new spur route from I-84 to Bristol.

Some online maps (including Google, below) have Route 320 continuing east from the I-84 interchange along Turnpike Road to end at Route 89 in Westford. However cool this might be (and it follows a very old alignment of Route 197), it isn't true.

• Route 320 Ends (Photos; Doug Kerr at state-ends.com)
• Route 320 - Google Maps

In the 1920s, state highway 320 followed today's Route 138, east of Route 12.

9.80 miles; from Route 69 in Wolcott to I-691 exit 4 in Southington.

In the 1920s, state highway 322 followed today's Route 152 in Orange.

Route 322 was commissioned in 1963, comprising the 4.3-mile north-south section only. In 1968, it gained another 1.7 miles, to I-84, when US 6A was decommissioned. When I-691 completed in late 1987, Route 322 inherited 3.8 more miles from Route 66.

Parts of Route 322 in Wolcott were formerly known as SR 522.

East-west section becomes part of restored Route 14.

• Route Change Notice, ConnDOT, Oct. 22, 1987.

• Route 322 Ends (Photos; Doug Kerr at state-ends.com)
• Route 322 - Google Maps

In the 1920s, state highway 323 followed today's Route 70 west of Route 10.

In the 1920s, state highway 325 followed today's Route 68 from Route 8 to Route 10.

In the 1920s, state highway 326 followed today's Route 120 in Southington.

As 1920s route numbers seemed to be assigned in order, with few gaps, the existence of routes 326, 328 and so on would imply the existence of a State Highway 324. However, I've seen no sign of one yet.

In the 1920s, state highway 327 followed today's Route 182 and 182A in Colebrook.

In the 1920s, state highway 328 followed today's Route 187, with an east connection to Route 75.

In the 1920s, state highway 329 followed today's Route 102.