Wikipedia:WikiProject U.S. Roads/Connecticut/List of 1920s numbers

The main source for this list is the 1926 maps at [1].

Routes 1-99

Route 1, NY to RI via New Haven, New London
- Now U.S. Route 1
Route 2
- Now U.S. Route 5
Route 3
- Now Route 35, U.S. Route 7, U.S. Route 6
Route 4, NY to MA via Sharon, Salisbury
- Now Route 343, Route 41
Route 8, Stratford to MA via Derby, Waterbury, Torrington, Winsted
- Now Route 110, Route 8
Route 10, Saybrook to MA via Middletown, Hartford, Granby
- Now Route 9, Route 99, Route 189, Route 10
Route 12
- Now Route 32, Route 12
Route 17, MA to west of Westerly via Canaan, Winsted, Hartford, Colchester, Norwich
- Now U.S. Route 7, U.S. Route 44, Route 2
Route 32
- Now Route 12, Route 32, Route 19

Routes 101-199

Route 101, South Chaplin to RI
- Now Route 198, US 44
Route 102, New London to Colchester
- Now Route 85
Route 103, Central Village to RI
- Now Route 14
Route 104, Middletown to Glastonbury
- Now Route 17
Route 105, Thompsonville to Stafford Springs
- Now Route 190
Route 106, Clinton to Higganum
- Now Route 81
Route 107, Talcottville to West Ashford
- Now Route 30 and Route 74
Route 108, South Manchester to MA
- Now Tolland Turnpike and Route 83
Route 109, Bolton Notch to Phoenixville
- Now US 44
Route 110, Hartford to MA
- Now Route 159
Route 111, Waterbury to Willimantic
- Now Meriden Road, Route 322, W. Main St, E. Main St, and Route 66
Route 112, Guilford to Middletown
- Now Route 77 and Route 17
Route 113, Plainville to Hartford
- Now Route 372, Route 71, and New Britain Ave
Route 114, New Haven to Durham
- Now Route 17
Route 115, Hartford to Weatogue
- Now Route 185
Route 116, Farmington to Granby via Simsbury
- Now Route 10
Route 117, New Haven to Sandy Hook
- Now Route 34
Route 118, New Haven to Milldale
- Now Route 10
Route 119, NY to Danbury
- Now US 6
Route 120, New Haven to Naugatuck
- Now Route 63
Route 121, NY to Canaan
- Now U.S. Route 44
Route 122, Newtown to Bridgeport
- Now Route 25
Route 123, Cornwall to Avon
- Now Route 4 and US 202
Route 124, Bridgeport to Danbury
- Now Route 58
Route 125, Southbury to New Milford
- Now Route 67
Route 126, Norwalk to Ridgefield
- Now US 7
Route 127, Bulls Bridge to NY
- Now Bulls Bridge Road
Route 128, Danbury to Torrington
- Now US 202
Route 129, Gaylordsville to NY
- Now Route 55
Route 130, Woodbury to Goshen
- Now Route 61, Route 63
Route 131, NY to Sherman
- Now Briggs Hill Road
Route 132, Cornwall to South Canaan
- Now Route 43, Route 63
Route 133, north of Winsted to Granby
- Now Route 20
Route 134, New Milford to Canaan
- Now US 7
Route 135, New Haven to North Branford
- Now Route 80, Route 139
Route 136, Danbury to Gaylordsville
- Now Route 37, Route 39
Route 137, Pomfret Landing to Killingly
- Now Route 101
Route 138, Farmington to Collinsville
- Now Route 4, Route 179
Route 139, Killingly to RI
- Now Route 101
Route 140, North Branford to North Guilford
- Now Route 80
Route 141, Willimantic to Plainfield
- Now Route 14, Route 14A
Route 142, Putnam to MA
- Now Route 171, Route 169
Route 143, Ridgefield to NY
- Now Route 116
Route 144, Wauregan to Brooklyn
- Now Route 205
Route 145, New Milford to Shelton
- old Ousatonic Turnpike (now gone)
Route 146, Mansfield Center to Storrs
- Now Route 195
Route 147, Woodbridge to Southbury
- Now Route 67
Route 148, East Haddam to North Westchester
- Now Route 149
Route 149, Stafford Springs to MA
- Now Route 190, Route 171
Route 150, Old Lyme to North Plain
- Now Route 156
Route 151, Willington to MA
- Now Route 320, Centre Pike, Route 197
Route 152, Washington to Cornwall
- Now Route 45
Route 153, East Haddam to Norwich
- Now Route 82
Route 154, Woodbury to Washington
- Now Route 47
Route 155, Bulls Bridge to New Preston
- Now Bulls Bridge Road, W. Meetinghouse Road, Barker Road, Cherniske Road
Route 156, Newtown to Brooksfield
- Now Route 25
Route 157, Bristol to Farmington
- Now US 6
Route 158, Redding Ridge to Newtown
- old Newtown Turnpike
Route 159, New Milford to Washington
- Now Route 109
Route 160, Unionville to Plainville
- Now Route 177
Route 161, Bethel to Newtown
- Now Route 302
Route 162, Berlin to New Britain
- Now Route 372, Route 71
Route 163, Torrington to Burlington
- Now Route 4
Route 164, Glastonbury to Manchester
- Now Route 83
Route 165, Glastonbury
- Now Route 94
Route 166, Vernon to Stafford
- Now Route 30
Route 167, Haddam
- Now Route 151
Route 168, Bozrah to Andover
- Now Route 87
Route 169, Chester
- Now Route 148
Route 170, Montville
- Now New London Turnpike (local)
Route 171, East Haven to Branford
- Now Route 142
Route 172, Waterbury to Bristol
- Now Route 69
Route 173, Shelton
- Now Route 110
Route 174, Winsted to MA
- Now Route 183

Routes 301-399

Route 312, Torrington to Norfolk
- Now Route 272