The Federal Aid Highway Act of 1968 authorized a 1500-mile increase in the nation's Interstate Highway System, bringing the total to 42,500 miles. Texas proposed I-27 from Amarillo to Lubbock in 1968 and received approval. The Bureau of Public Roads asked the other states to submit proposals for the available 1500 miles. The states however proposed a total of more than 11,000 miles. By April 1970, proposals for 9,400 miles were submitted at with an estimated cost of $13 billion. Some proposals became actual Interstate routes like I-540 in northwest Arkansas, which later was redesignated as I-49, and US 78 ADHS Corridor X from Memphis to Birmingham that has since been completed as I-22.

Source document: "Report on the Status of the Federal-Aid Highway Program", Hearing before the Subcommittee on Roads of the Committee on Public Works, U. S. Senate; dated April 15, 1970; pages 89-91.

State Route Miles Completed/Future Interstate Route or Route Concept Replacement
AL Mobile Connector, I-65 to I-10 6.2 Completed as I-165, connection to I-10 was cancelled
AL Birmingham toward Memphis 91.3 Completed as I-22
AZ Phoenix "loop" freeway system 63.3 Completed as Loop 303, Loop 101, Loop 202 South Mountain Freeway
AZ Three urban freeways in Tucson 31.0 Never built, bypass concept replaced by Future I-11
AR Little Rock to Dumas 77.3 Replaced by "I-69 Spur" concept combining the existing I-530 to Pine Bluff and AR 530 to Future I-69 near Monticello
AR US 67 Little Rock to Newport 79.0 Completed as US 67 freeway from I-40 Little Rock to Walnut Ridge, redesignated as Future I-57 to US 60 in Poplar Bluff, Missouri then to I-57/I-55 in Sikeston Missouri
AR Gilmore to Walnut Ridge 64.5 Completed as I-555
AR Van Buren to Rogers 60.5 Completed as I-540, redesignated as I-49
AR Texarkana toward Shreveport 33.5 Completed as I-49
CA Fremont to Hayward 15.2 Cancelled CA 238 freeway.  Unused ramps at I-680 removed 2002.
CA San Bernardino bypass, I-10 to I-15 14.2 Never built
CA "Future I-210 East Extension" from existing I-210 to I-15 (formerly CA 31) 19.2 Completed as non-interstate standard freeway CA 210
CA US 50 Sacramento to Reno 99.9 Never built, potential "Future I-70" Trans America Corridor
CA SF Bay crossing and connectors 24.9 Newly proposed "Southern San Franciso Bay Bridge Crossing"
CA "Future I-40" West Extension using CA 58 Buttonwillow to Barstow via Bakersfield 145.0 Never built
C0 Northwest quadrant of Denver C-470 Outer Belt 24.8 Concept was cancelled because of local opposition
DE US 13 Wilmington to Norfolk Virginia 79.0 Never built
FL Miami to Homestead 32.0 Completed as local toll-road
FL West of Miami to Homestead AFB 20.0 Completed as local toll-road
GA Macon connector, I-475 to I-16 8.0 Never built
GA Augusta circumferential 15.0 Completed as I-520
GA Savannah spur 3.4 Completed as I-516
HI Honolulu south loop 6.5 Completed as H-1
ID Boise, east connector 0.6 Never built
ID I-15 near McCammon to Wyo. state line en route to I-80 87.0 Never built
IL DuPage Cty, I-55 to I-90 19.0 Completed as I-355
IL Hennepin to Peoria 44.0 Never built
IN Indy, Northeast Expressway 8.7 Never built
IN US 41 I-70 in Terre Haute to I-64 92.1 Never built, concept replaced by I-69 Evansville to Indianapolis
IN Evansville to Ky. state line 6.8 Never built, concept replaced by I-69
IN I-94 to I-65 connector 10.1 Completed as I-294
IA US 218 Cedar Falls to Mason City 84.1 Completed as non-interstate expressway "Avenue of the Saints"
IA US 20 Dubuque to Cedar Falls 134.2 Completed as non-interstate freeway and four-lane expressway
IA US 218 Iowa City to Keokuk 88.2 Completed as non-interstate expressway "Avenue of the Saints"
IA Des Moines, southeast belt 24.5 Completed as non-interstate freeway IA-5
IA US 151 Cedar Rapids, southwest to I-80 33.3 Never built
IA US 34 Des Moines to Burlington 151.6 Completed as four-lane expressway with non-interstate freeway bypasess
IA US 20 Sioux City to I-35 143.9 Completed as non-interstate freeway and four-lane expressway
IA US 61 Davenport to Dubuque 66.3 Never built
IA Independence diagonal route 23.5 Never built
KS US 69 Kansas City Kansas to Okla. state lines 138.7 Concept replaced by I-49 following US 71 in Missouri, northern part completed as non-interstate freeway to Fort Scott,
KS US 54 Wichita to Okla. state line en route to Tucumcari, NM 216.7 "Future I-66" Trans America Highway cancelled in 2015
KS US 400 Wichita to Pittsburg 144.6 "Future I-66" Trans America Highway cancelled in 2015
KS US 169 Olathe to Okla. state line en route to Tulsa 157.4 Never built
KS US 36 Belleville to Mo. state line en route to St. Joseph 152.0 Never built
KS US 75 from I-35 in Olivet to Topeka 41.5 Never built
KS US 59 Ottawa to I-70 in Lawrence 26.4 Never built
KS Wichita northeast belt 10.0 Completed as non-interstate KS 96 freeway
KY Jefferson Fwy, Louisville 34.7 Never built
KY Crosstown Fwy, Lexington 9.8 Never built
KY Ind. state line to Henderson 5.4 Concept replaced by Future I-69
LA New Orleans to Shreveport 341.6 Completed as I-49 Shreveport to Lafayette between 1980-1996, now Future I-49 Corridor from Kansas City MO to New Orleans LA
ME Topsham to Brunswick 3.8 Never built
ME "Future I-98" Bangor to Calais 119.1 Never built
ME Augusta belt 5.9 Never built
ME Houlton to Van Buren 77.5 Never built
ME Pittsfield (I-95) to NH state line near Gilead 94.8 Never built
MD MD 295 Baltimore to Washington Parkway 27.0 Never built
MD Baltimore to Annapolis 20.5 Completed as I-97
MD I-70 in Hancock to Cumberland 31.1 Completed as I-68
MD US 13, Norfolk - Wilmington route 32.0 Never built
MD Annapolis to Dover Delaware 45.0 Never built
MA Haverhill, downtown connector 2.0 Never built
MA Beverly - Salem - Vinnin Square 8.1 Never built
MA Lawrence connector 3.0 Never built
MA US 7 Pittsfield to I-90 11.0 Never built
MA Worcester - Fitchburg 32.6 Completed as I-190
MI Detroit inner loop 9.0 Never built
MI I-275 extension to I-75 21.0 Never Built
MI Flint to Port Huron 60.0 Completed as I-69
MI US 131 from I-96 Grand Rapids to I-75 Mackinaw City 210.0 Completed as non-interstate freeway to Manton,
potential "Future I-67", "Future I-63", or "Future I-73"
MI US 23 Standish to Cheboygan 184.0 Never built
MN I-35 Extension to Duluth 5.4 Completed as I-35
MS US 78, Birmingham to Memphis route 120.3 Completed as I-22
MO "Future I-755" St. Louis inner belt 4.5 Never built
MO US 63 Columbia via Jefferson City to Rolla 86.3 Never built
NE "Future I-135" I-80 near York Kansas border to Salina 57.2 Never built
NE US 281 I-80 to Grand Island 6.9 Never built
NE US 281 I-80 to Hastings 16.9 Never built
NE US 77 Lincoln to S. Sioux City 120.8 Never built
NE Omaha to North Bend 42.6 Never built
NV Reno to Carson City 32.3 Completed as I-580
NV Las Vegas Spur 10.5 Completed as I-515 now part of Future I-11 Corridor
NV US 50 California border to Utah border, via Carson City 403.7 Never built, potential "I-70" Transamerica Corridor
NH "Future I-92" Albany to Portsmouth 103.0 Never built
NH "Future I-98" Glens Falls to Calais 44.0 Never built
NH Future I-190 north extension Manchester to Worcester Mass. 31.0 Never built
NJ NJ 75 Newark, I-78 to I-280 3.0 Never built
NJ US 1 Elizabeth to Newark 6.0 Never built
NJ NJ 85 Jersey City, I-78 to I-495 3.0 Never built
NJ NJ 3/US 46 New Durham to Wayne 35.1 Never built
NJ NJ 90 Delair (Pa. state line) to I-295 7.5 Never built
NJ US 322 Bridgeport (Pa. state line) to I-295 4.0 Never built
NJ Morristown to Springfield 15.0 Never built
NJ Franklin Lakes to NY state line near Alpine 16.7 Never built
NJ Hope to NY state line near Port Jervis 34.0 Never built
NM US 70 Las Cruces to Texico 301.0 Never built
NY Sheridan Expwy 4.0 Completed as I-895
NY NYC, Co-op City I-678 Bypass 2.9 Never built
NY Binghamton to Rochester 162.0 Completed as I-390
NY US 219 Buffalo to Pa. state line near Bradford 64.4 Never built
NY Binghamton - Erie 150.5 Completed as I-86
NY Watertown - Burlington 150.0 Never built
NY Future I-92 Schenectady to Vermont state line then Portsmouth, NH 26.1 Never built
NY Syracuse north belt 12.0 Never built
NY Future I-98 Glens Falls to Vermont state line en route to Bangor 33.0 Never built
NY NY 13 Elmira - Courtland 49.0 Never built
NY Rochester Outer Belt 42.5 Never built
NY Oyster Bay - Long Island expwys 36.0 Planning for Future I-287 Long Island Sound Crossing was cancelled in 2018
NY NY 17 Binghamton to New York City 132.0 Never built
NY West Dutchess Expwy 69.0 Never built
NY US 209 Catskill Expressway 60.5 Never built
NY NY 18 "Future I-990" Niagara Falls - Rochester 66.3 Never built
NY Lockport Expwy 12.0 Completed as I-990
NY Buffalo - Dansville 61.0 Never built
NY Yonkers - NJ expwy 2.0 Never built
NY Delaware - St Lawrence expwy 212.0 Never built
NY Amsterdam - Northway expwy 20.0 Never built
NC Asheville, north belt 8.8 Never built
NC Charlotte, outer belt 71.5 Completed as I-485
NC Winston - Salem to Greensboro 42.8 Never built
NC Greensboro spur 7.6 Never built
NC High Point to I-40 west of Greensboro 13.0 Never built
NC Durham, east connector to I-85 5.8 Never built
NC Raleigh spur 2.0 Never built
NC Fayetteville, north and south bypasses 25.0 Never built
NC US 421 Greensboro to Wilmington 159.0 Concept replaced by existing I-40 extension
NC Morehead City spur 83.0 Future I-42
NC US 74 Asheville - Charlotte - Wilmington 245.4 Completed as freeway, toll-road, four-lane highway, and I-74
OH Cleveland connector, I-71 to I-90 6.3 Never built
OH I-675 Dayton West Bypass 19.8 West bypass cancelled, I-675 Eastern Bypass completed 1986
OH Akron - Canton connectors 67.2 Never built
OH Toledo Connector, I-75 to I-280 3.6 Never built
OK Okla City, spur to Will Rogers Airport 2.2 Never built
OK Tulsa to Tonkawa (at I-35) 108.4 Never built
OK Tulsa to Webbers Falls (at I-40) 63.7 Never built
OR Portland to Astoria (near Pac. coast) 100.9 Cancelled Future I-505
OR Salem 2.3 Completed as I-305
OR Eugene, 4.2 Completed as I-105
PA US 219 Ebensburg to NY state line en route to Buffalo 115.0 Never built
PA Harrisburg, West Shore Expwy 6.0 Never built
PA Allentown spur 7.0 Completed as I-178
PA Bethelehum spur 4.0 Completed as I-378
PA PA 309 Wilkes-Barre spur 2.5 Never built
SC Columbia, connector to I-26 1.5 Never built
SD US 83, I-90 to Pierre 34.5 Never built
TN Memphis, Riverfront - NW Expwy 8.9 Never built
TN Chattanooga, Central Fwy 8.6 Never built
TN Dyersburg to Clarksville, I-155 to I-24 125.0 Never built, potential "Future I-48" Corridor following US 412 to Oklahoma
TN Dyersburg to Jackson, I-155 to I-40 40.0 Never built, route concept replaced by Future I-69
TN Memphis toward Birmingham, AL 9.0 Completed as I-22
TX Lubbock to Roscoe 111.0 Proposed Future I-27 Plains to Ports Corridor
UT Salt Lake City, loop and radial 12.5 Never built
UT Lagoon (I-15) to Uintah Jct (I-84) 10.9 Never built
UT US 6 Green River to Spanish Fork 126.4 Never built
VT "Future I-92" Albany to Portsmouth 45.2 Never built
VT "Future I-98" Glens Falls to Calais 97.3 Never built
VA Richmond, extend I-195 to I-95 3.3 Never built
VA Portsmouth - Norfolk connector 8.0 Never built
VA Richmond, west belt 30.0 Completed as VA 288
VA Norfolk, extend I-464 to I-264 0.6 I-464 Downtown Tunnel/Berkley Bridge; I-264 completed 1978
WA Tacoma, north loop 10.6 Never built
WV "Future I-66" west extension from I-79 Weston to I-81 Stasburg, Va. 128.1 Completed and under construction as US 48 Corridor H expressway
WI Beloit to Milwaukee 59.8 Completed as I-43
WI Milwaukee Belt 40.7 Never built
WI US 53 Eau Claire to Superior 151.7 Completed as non-interstate freeway and expressway