Route 85 (Connecticut) was commissioned from the old turnpike in 1932 .

Route 320 was commissioned in 1963 from former SR 520 and has had no significant changes since.

Route 315 was commissioned from former SR 915 in 1963.

Route 33 was commissioned in 1932 from parts of former 1920s state highways 304 and 176.

Route 128 was commissioned in 1965, taking over a small part of the former Route 30.

Route 155 was commissioned in 1933 or 1934 as an additional connection between Routes 9 and 17.

Route 126 was commissioned in 1965 to replace the former route 33.

Route 317 was commissioned in 1964 from SR 517, and has had no significant changes since.

Route 364 was commissioned from SR 564 in 1963 and has had no significant changes since.

Route 118 was commissioned in 1965 to replace the former route 36.