All the 3-digit interstates
Here are all the authenticated route numbers I've seen used for 3-digit interstates, existing or proposed. "Authenticated" means not just a rumor: generally, one of the following:

• Exists today
• approved by AASHTO or the FHWA
• appeared on an official highway map
• proposed by a governmental organization

If a route number is in parentheses, it's not a current interstate. There could be a number of reasons for this, including:

• It was cancelled (like I-895) around Providence)
• It has a different number now (like I-479, which is now I-579)
• It is a proposed or future interstate (like I-905 in southern California)

To find a route, either type the number in the search box to the left, or see the listing by state below.

After the state listing, the 3di's are grouped and totaled by category.

State	Highways
Alabama	165 (210) 359 459 565 759
Arkansas	(130) 430 440 530 540 (555) 630 (730) (740)
Arizona	(410) (510) (710)
California	(102) (105) 105 (106) (109) (110) (110) 110 (112) (113) (115) (180) 205 210 215 238 280 305 380 405 (480) 505 580 605 680 710 780 805 (880) 880 (905) 980
Colorado	225 270 (425) (470)
Connecticut	(284) 291 384 395 (484) (491) 684 691
Washington, D. C.	(266) 295 395 695
Delaware	295 495 (895)
Florida	110 175 195 275 295 375 395 595 (795)
Georgia	(175) 185 285 (420) (475) 475 (485) 516 520 575 675 985
Hawaii	H-201
Iowa	129 235 (274) 280 (380) 380 480 680
Idaho	184
Illinois	155 172 180 190 255 270 (274) 280 290 294 355 474 (494) (694) (870)
Indiana	164 (165) 265 275 465 469 865 (875)
Kansas	135 235 335 435 470 635 670
Kentucky	(175) 264 265 275 (875)
Louisiana	110 210 220 (310) 310 (410) (410) (420) 510 610 910
Massachusetts	190 195 290 291 295 391 395 495 (695) (895)
Maryland	(170) 195 (197) 270 295 (297) 370 395 495 (595) 595 695 795 895
Maine	195 295 395 495
Michigan	194 196 275 296 375 (394) 475 496 675 696
Minnesota	(335) 394 494 535 694 (894)
Missouri	(144) 155 170 229 (244) 255 270 (370) 435 470 635 670
Mississippi	110 220 (269) (669)
Montana	115 315
North Carolina	(140) (140) (185) (195) 240 277 (285) (295) 440 485 540 (640) (785) (795) (840)
North Dakota	194
Nebraska	129 180 (280) 480 (580) 680
New Hampshire	(193) 293 393
New Jersey	195 278 280 287 295 676 (695) (895) (895)
Nevada	215 515 (580)
New York	(178) (187) 190 278 (281) 287 290 295 (381) (386) (387) 390 478 481 (486) (487) (487) 490 495 587 590 678 684 (687) 690 695 787 790 878 890 895 990
Ohio	(177) 270 271 275 277 280 (290) 470 471 475 480 490 670 675 680 (875)
Oklahoma	235 240 244 (440) 444
Oregon	105 205 (305) 405 (505)
Pennsylvania	176 (178) (179) (180) 180 276 279 (280) 283 376 (378) (380) 380 (395) 476 (479) (480) (495) (576) 579 676 (680) (695) (876) (895) (895)
Rhode Island	(184) 195 295 (895)
South Carolina	126 (174) 185 (277) (326) 385 520 526 585
South Dakota	190 229
Tennessee	124 (126) 140 155 (169) (175) 181 240 (255) (265) (269) 275 440 (475) 640 (669) (840)
Texas	110 345 410 610 635 820
Utah	215 (415)
Virginia	195 264 (266) 295 (364) 381 (385) 395 464 495 564 581 (595) 664 (785) (795) (795) (864)
Vermont	189 (289)
Washington	182 205 405 (605) 705
Wisconsin	535 794 894
West Virginia	470
Wyoming	180

p class="first">Current 3di's by parent

I-H-1: 201 
I-5: 105(x2) 205(x2) 305 405(x3) 505 605 705 805 
I-10: 110(x5) 210(x2) 310 410 510 610(x2) 710 910 
I-15: 115 215(x3) 315 515 
I-16: 516 
I-20: 220(x2) 520 820 
I-24: 124 
I-25: 225 
I-26: 126 526 
I-29: 129 229(x2) 
I-30: 430 530 630 
I-35: 135 235(x3) 335 435 535 635(x2) 
I-38: 238 
I-40: 140 240(x3) 440(x3) 540(x2) 640 
I-44: 244 444 
I-45: 345 
I-55: 155(x2) 255 355 
I-59: 359 459 759 
I-64: 164 264(x2) 464 564 664 
I-65: 165 265(x2) 465 565 865 
I-69: 469 
I-70: 170 270(x4) 370 470(x3) 670(x2) 
I-71: 271 471 
I-72: 172 
I-74: 474 
I-75: 175 275(x4) 375(x2) 475(x3) 575 675(x3) 
I-76: 176 276 376 476 676 
I-77: 277(x2) 
I-78: 278 478 678 878 
I-79: 279 579 
I-80: 180(x4) 280(x4) 380(x3) 480(x2) 580 680(x3) 780 880 980 
I-81: 181 381 481 581 
I-82: 182 
I-83: 283 
I-84: 184 384 684 
I-85: 185(x2) 285 385 485 585 985 
I-87: 287 587 787 
I-89: 189 
I-90: 190(x4) 290(x3) 390 490(x2) 590 690 790 890 990 
I-91: 291(x2) 391 691 
I-93: 293 393 
I-94: 194(x2) 294 394 494 694 794 894 
I-95: 195(x6) 295(x7) 395(x5) 495(x5) 595(x2) 695(x3) 795 895(x2) 
I-96: 196 296 496 696 

All 3di's (including cancelled, etc) by parent

I-H-1: 201 
I-2: 102 
I-5: 105(x3) 205(x2) 305(x2) 405(x3) 505(x2) 605(x2) 705 805 905 
I-6: 106 
I-9: 109 
I-10: 110(x7) 210(x3) 310(x2) 410(x4) 510(x2) 610(x2) 710(x2) 910 
I-12: 112 
I-13: 113 
I-15: 115(x2) 215(x3) 315 415 515 
I-16: 516 
I-20: 220(x2) 420(x2) 520 820 
I-24: 124 
I-25: 225 425 
I-26: 126(x2) 326 526 
I-29: 129 229(x2) 
I-30: 130 430 530 630 730 
I-35: 135 235(x3) 335(x2) 435 535 635(x2) 
I-38: 238 
I-40: 140(x3) 240(x3) 440(x4) 540(x2) 640(x2) 740 840(x2) 
I-44: 144 244(x2) 444 
I-45: 345 
I-55: 155(x2) 255(x2) 355 555 
I-59: 359 459 759 
I-64: 164 264(x2) 364 464 564 664 864 
I-65: 165(x2) 265(x3) 465 565 865 
I-66: 266 
I-69: 169 269 469 669 
I-70: 170(x2) 270(x4) 370(x2) 470(x4) 670(x2) 870 
I-71: 271 471 
I-72: 172 
I-74: 174 274 474 
I-75: 175(x3) 275(x4) 375(x2) 475(x5) 575 675(x3) 875 
I-76: 176 276 376 476 576 676 876 
I-77: 177 277(x3) 
I-78: 178(x2) 278 378 478 678 878 
I-79: 179 279 479 579 
I-80: 180(x6) 280(x6) 380(x5) 480(x4) 580(x3) 680(x4) 780 880(x2) 980 
I-81: 181 281 381(x2) 481 581 
I-82: 182 
I-83: 283 
I-84: 184(x2) 284 384 484 684 
I-85: 185(x3) 285(x2) 385(x2) 485(x2) 585 785 985 
I-86: 386 486 
I-87: 187 287 387 487(x2) 587 687 787 
I-89: 189 289 
I-90: 190(x4) 290(x4) 390 490(x2) 590 690 790 890 990 
I-91: 291(x2) 391 491 691 
I-93: 193 293 393 
I-94: 194(x2) 294 394(x2) 494(x2) 694(x2) 794 894(x2) 
I-95: 195(x7) 295(x8) 395(x6) 495(x6) 595(x4) 695(x6) 795(x5) 895(x6) 
I-96: 196 296 496 696 
I-97: 197 297 

3di counts by status

Signed and built: 223
I-105 (ca)
I-105 (or)
I-110 (ca)
I-110 (fl)
I-110 (la)
I-110 (ms)
I-115 (mt)
I-126 (sc)
I-129 (ia ne)
I-135 (ks)
I-140 (tn)
I-155 (il)
I-155 (mo tn)
I-164 (in)
I-165 (al)
I-170 (mo)
I-172 (il)
I-175 (fl)
I-176 (pa)
I-180 (il)
I-180 (ne)
I-180 (pa)
I-180 (wy)
I-181 (tn)
I-182 (wa)
I-184 (id)
I-185 (ga)
I-185 (sc)
I-189 (vt)
I-190 (il)
I-190 (ma)
I-190 (ny)
I-190 (sd)
I-194 (mi)
I-195 (fl)
I-195 (ma ri)
I-195 (md)
I-195 (me)
I-195 (nj)
I-195 (va)
I-196 (mi)
I-H-201 (hi)
I-205 (ca)
I-205 (or wa)
I-210 (ca)
I-210 (la)
I-215 (ca)
I-215 (nv)
I-215 (ut)
I-220 (la)
I-220 (ms)
I-225 (co)
I-229 (mo)
I-229 (sd)
I-235 (ia)
I-235 (ks)
I-235 (ok)
I-238 (ca)
I-240 (nc)
I-240 (ok)
I-240 (tn)
I-244 (ok)
I-255 (il mo)
I-264 (ky)
I-264 (va)
I-265 (in)
I-265 (ky)
I-270 (co)
I-270 (md)
I-270 (mo il)
I-270 (oh)
I-271 (oh)
I-275 (fl)
I-275 (mi)
I-275 (oh in ky)
I-275 (tn)
I-276 (pa)
I-277 (nc)
I-277 (oh)
I-278 (ny nj)
I-279 (pa)
I-280 (ca)
I-280 (il ia)
I-280 (nj)
I-280 (oh)
I-283 (pa)
I-285 (ga)
I-287 (ny nj)
I-290 (il)
I-290 (ma)
I-290 (ny)
I-291 (ct)
I-291 (ma)
I-293 (nh)
I-294 (il)
I-295 (dc md)
I-295 (fl)
I-295 (ma ri)
I-295 (me)
I-295 (nj de)
I-295 (ny)
I-295 (va)
I-310 (la)
I-335 (ks)
I-355 (il)
I-359 (al)
I-370 (md)
I-375 (fl)
I-375 (mi)
I-376 (pa)
I-380 (ca)
I-380 (ia)
I-380 (pa)
I-381 (va)
I-384 (ct)
I-385 (sc)
I-390 (ny)
I-391 (ma)
I-393 (nh)
I-394 (mn)
I-395 (ct ma)
I-395 (dc va)
I-395 (fl)
I-395 (md)
I-395 (me)
I-405 (ca)
I-405 (or)
I-405 (wa)
I-410 (tx)
I-430 (ar)
I-435 (ks mo)
I-440 (ar)
I-440 (nc)
I-440 (tn)
I-459 (al)
I-464 (va)
I-465 (in)
I-469 (in)
I-470 (ks)
I-470 (mo)
I-470 (wv oh)
I-471 (oh)
I-474 (il)
I-475 (ga)
I-475 (mi)
I-475 (oh)
I-476 (pa)
I-480 (ia ne)
I-480 (oh)
I-481 (ny)
I-485 (nc)
I-490 (ny)
I-490 (oh)
I-494 (mn)
I-495 (de)
I-495 (ma)
I-495 (md va)
I-495 (ny)
I-496 (mi)
I-505 (ca)
I-510 (la)
I-515 (nv)
I-516 (ga)
I-520 (ga sc)
I-526 (sc)
I-530 (ar)
I-535 (mn wi)
I-540 (ar)
I-540 (nc)
I-564 (va)
I-565 (al)
I-575 (ga)
I-579 (pa)
I-580 (ca)
I-581 (va)
I-585 (sc)
I-587 (ny)
I-590 (ny)
I-595 (fl)
I-605 (ca)
I-610 (la)
I-610 (tx)
I-630 (ar)
I-635 (ks mo)
I-635 (tx)
I-640 (tn)
I-664 (va)
I-670 (ks mo)
I-670 (oh)
I-675 (ga)
I-675 (mi)
I-675 (oh)
I-676 (pa nj)
I-678 (ny)
I-680 (ca)
I-680 (ia ne)
I-680 (oh)
I-684 (ny ct)
I-690 (ny)
I-691 (ct)
I-694 (mn)
I-695 (md)
I-695 (ny)
I-696 (mi)
I-705 (wa)
I-710 (ca)
I-759 (al)
I-780 (ca)
I-787 (ny)
I-790 (ny)
I-794 (wi)
I-795 (md)
I-805 (ca)
I-820 (tx)
I-865 (in)
I-880 (ca)
I-890 (ny)
I-894 (wi)
I-895 (md)
I-895 (ny)
I-980 (ca)
I-985 (ga)
I-990 (ny)
----
Not signed as interstate: 14
I-110 (tx)
I-124 (tn)
I-194 (nd)
I-296 (mi)
I-305 (ca)
I-315 (mt)
I-345 (tx)
I-444 (ok)
I-478 (ny)
I-495 (me)
I-595 (md)
I-695 (dc)
I-878 (ny)
I-910 (la)
----
Proposed: 14
I-169 (tn)
I-174 (sc)
I-175 (ky tn)
I-269 (tn ms)
I-285 (nc)
I-295 (nc)
I-370 (mo)
I-394 (mi)
I-475 (tn)
I-576 (pa)
I-605 (wa)
I-730 (ar)
I-875 (oh ky in)
I-905 (ca)
----
Future: 8
I-130 (ar)
I-140 (nc)
I-555 (ar)
I-580 (nv)
I-785 (va nc)
I-795 (fl)
I-840 (nc)
I-840 (tn)
----
Cancelled: 39
I-165 (in)
I-170 (md)
I-175 (ga)
I-178 (pa)
I-184 (ri)
I-197 (md)
I-266 (va dc)
I-284 (ct)
I-289 (vt)
I-290 (oh)
I-297 (md)
I-305 (or)
I-310 (la)
I-335 (mn)
I-410 (la)
I-410 (la)
I-420 (ga)
I-420 (la)
I-475 (ga)
I-480 (ca)
I-484 (ct)
I-485 (ga)
I-487 (ny)
I-491 (ct)
I-494 (il)
I-505 (or)
I-510 (az)
I-595 (md)
I-595 (va)
I-687 (ny)
I-694 (il)
I-695 (ma)
I-695 (nj)
I-695 (pa)
I-710 (az)
I-740 (ar)
I-864 (va)
I-895 (nj pa)
I-895 (ri ma)
----
Decommissioned: 5
I-105 (ca)
I-110 (ca)
I-378 (pa)
I-580 (ne)
I-880 (ca)
----
Built as non-interstate: 1
I-470 (co)
----
Numbered as another interstate: 36
I-126 (tn)
I-179 (pa)
I-180 (ca)
I-180 (pa)
I-193 (nh)
I-210 (al)
I-244 (mo)
I-255 (tn)
I-265 (tn)
I-274 (il ia)
I-280 (ne)
I-280 (pa)
I-281 (ny)
I-326 (sc)
I-380 (ia)
I-380 (pa)
I-385 (va)
I-395 (pa)
I-410 (az)
I-415 (ut)
I-425 (co)
I-440 (ok)
I-479 (pa)
I-480 (pa)
I-486 (ny)
I-487 (ny)
I-495 (pa)
I-640 (nc)
I-669 (tn ms)
I-680 (pa)
I-795 (va)
I-870 (il)
I-876 (pa)
I-894 (mn)
I-895 (de)
I-895 (nj pa)
----
Preliminary numbering: 14
I-102 (ca)
I-106 (ca)
I-109 (ca)
I-110 (ca)
I-112 (ca)
I-113 (ca)
I-115 (ca)
I-144 (mo)
I-177 (oh)
I-178 (ny)
I-187 (ny)
I-364 (va)
I-381 (ny)
I-387 (ny)
----
Proposed number rejected: 3
I-140 (nc)
I-185 (nc)
I-195 (nc)
----
Unknown history: 4
I-277 (sc)
I-386 (ny)
I-795 (nc)
I-795 (va)
----

Total: 361

Astoundingly rococo trivia
A state can boast of a "balanced team effort" if all its 2-digit interstates also have associated 3-digit interstates in the state. For example, both I-35 and I-70, Kansas's only 2-digit interstates, have 3di's such as I-135 and I-470. The list of such states is small; larger states with plenty of interstates (Illinois, New York, California) tend to have 2di's that don't contribute with 3di's (I-57, I-88, I-40).

Here are the "team effort states", with number of 2dis:

• One 2di: Delaware, Maine, Rhode Island (all I-95 as well)
• Two 2di's: Kansas, Nevada (unsigned I-580), North and South Dakota
• Three 2di's: Arkansas (with new I-555), Connecticut, Oklahoma
• Four 2di's: New Jersey (I-76, 78, 80, 95, 676, 278, 280, 295, and more)

If you count any 3di's in state as matches, whether planned, existing, or cancelled, Tennessee wins with I-24, I-26, I-55, I-65, I-75, and I-81 all sporting real or proposed 3di's at one time or another.