US Interstate Numbers Table
| Route | Length (mi) | S/W terminus | N/E terminus | Formed |
|---|---|---|---|---|
| I-2 | 46 | La Joya, TX | Harlingen, TX | 2013 |
| I-4 | 132 | Tampa, FL | Daytona Beach, FL | 1957 |
| I-5 | 1,381 | San Diego, CA | Blaine, WA | 1957 |
| I-8 | 350 | San Diego, CA | Casa Grande, AZ | 1964 |
| I-10 | 2,460 | Santa Monica, CA | Jacksonville, FL | 1957 |
| I-11 | 54 | the Arizona state line | Las Vegas, NV | 2017 |
| I-12 | 85 | Baton Rouge, LA | Slidell, LA | 1967 |
| I-14 | 25 | Copperas Cove, TX | Belton, TX | 2017 |
| I-15 | 1,433 | San Diego, CA | Sweetgrass, MT | 1957 |
| I-16 | 166 | Macon, GA | Savannah, GA | 1966 |
| I-17 | 145 | Phoenix, AZ | Flagstaff, AZ | 1961 |
| I-19 | 63 | Nogales, AZ | Tucson, AZ | 1972 |
| I-20 | 1,539 | Reeves County, TX | Florence, SC | 1957 |
| I-22 | 202 | Byhalia, MS | Birmingham, AL | 2012 |
| I-24 | 316 | Pulley's Mill, IL | East Ridge, TN | 1962 |
| I-25 | 1,061 | Las Cruces, NM | Buffalo, WY | 1957 |
| I-26 | 328 | Asheville, NC | Charleston, SC | 1960 |
| I-27 | 128 | Lubbock, TX | Amarillo, TX | 1969 |
| I-29 | 750 | Kansas City, MO | Pembina, ND | 1957 |
| I-30 | 366 | northeast of Aledo, TX | North Little Rock, AR | 1957 |
| I-31 | — | Fargo, ND | Pembina, ND | 1957 |
| I-35 | 1,569 | Columbus, MN | Duluth, MN | 1956 |
| I-37 | 143 | Corpus Christi, TX | San Antonio, TX | 1959 |
| I-39 | 306 | Normal, IL | 29 west of Rothschild, WI | 1984 |
| I-40 | 2,556 | Barstow, CA | Wilmington, NC | 1957 |
| I-41 | 175 | Russell, IL | Howard, WI | 2015 |
| I-42 | 10 | near Tontitown, AR | Springdale, AR | 2026 |
| I-43 | 191 | Beloit, WI | Howard, WI | 1981 |
| I-44 | 636 | Wichita Falls, TX | St. Louis, MO | 1957 |
| I-45 | 284 | Galveston, TX | Dallas, TX | 1971 |
| I-49 | 547 | Alma, AR | Kansas City, MO | 1984 |
| I-55 | 964 | LaPlace, LA | Chicago, IL | 1960 |
| I-57 | 508 | Sikeston, MO | Chicago, IL | 1965 |
| I-59 | 445 | Slidell, LA | Wildwood, GA | 1960 |
| I-64 | 963 | Wentzville, MO | Chesapeake, VA | 1961 |
| I-65 | 887 | Mobile, AL | Gary, IN | 1958 |
| I-66 | — | Wichita, KS | Near Pikeville, KY | 1991 |
| I-68 | 113 | Morgantown, WV | Hancock, MD | 1991 |
| I-69 | 910 | Evansville, IN | Port Huron, MI | 1957 |
| I-70 | 2,171 | Cove Fort, UT | Woodlawn, MD | 1956 |
| I-71 | 345 | Louisville, KY | Cleveland, OH | 1959 |
| I-72 | 179 | Hannibal, MO | Champaign, IL | 1970 |
| I-73 | 101 | 74/US 74 Bus. west of Rockingham, NC | 68 northeast of Stokesdale, NC | 1997 |
| I-74 | 541 | Maxton, NC | NCUS 74 southwest of Lumberton, NC | 1974 |
| I-75 | 1,786 | Miami Lakes, FL | Sault Ste. Marie, MI | 1958 |
| I-76 | 187 | Arvada, CO | Big Springs, NE | 1975 |
| I-77 | 610 | Cayce, SC | Cleveland, OH | 1958 |
| I-78 | 146 | Union Township, PA | New York, NY | 1957 |
| I-79 | 343 | Charleston, WV | Erie, PA | 1967 |
| I-80 | 2,900 | San Francisco, CA | Teaneck, NJ | 1956 |
| I-81 | 855 | Dandrige, TN | Wellesley Island, NY | 1961 |
| I-82 | 143 | Ellensburg, WA | Hermiston, OR | 1957 |
| I-83 | 85 | Baltimore, MD | 322 north of Progress, PA | 1959 |
| I-84 | 769 | Portland, OR | Echo, UT | 1980 |
| I-85 | 666 | Montgomery, AL | Petersburg, VA | 1958 |
| I-86 | 62 | 30 northeast of Declo, ID | Chubbuck, ID | 1980 |
| I-87 | 12 | Raleigh, NC | Wendell, NC | 2017 |
| I-88 | 140 | northeast of East Moline, IL | Hillside, IL | 1987 |
| I-89 | 191 | Bow, NH | Highgate, VT | 1960 |
| I-90 | 3,099 | Seattle, WA | Boston, MA | 1956 |
| I-91 | 290 | New Haven, CT | Derby Line, VT | 1958 |
| I-93 | 189 | Canton, MA | Waterford, VT | 1957 |
| I-94 | 1,555 | Lockwood, MT | Port Huron, MI | 1956 |
| I-95 | 1,905 | Miami, FL | Houlton, ME | 1957 |
| I-96 | 192 | Norton Shores, MI | Detroit, MI | 1959 |
| I-97 | 17 | Parole, MD | Brooklyn Park, MD | 1987 |
| I-99 | 161 | Williamsport, PA | Painted Post, NY | 1998 |
Interstate numbers are the most legible grid in American travel: one-digit and two-digit routes are the mainlines, odd numbers run north-south and even numbers east-west, and the system's spine is the 0-and-5 club - I-10, I-20, I-40, I-80, I-90 across the map; I-5, I-15, I-25, I-35, I-95 up and down it. The scheme was designed as a mirror of the older US Routes: I-5 hugs the west coast where US 1 hugs the east, I-10 runs the southern rim where US 10 ran the north, so the two grids never collide on direction.
The lengths make the table a geography lesson: I-90 alone covers 3,100 miles from Boston to Seattle, I-80 crosses eleven states along the old rail corridors, and at the other end I-42 is a 10-mile North Carolina connection and I-2 runs 46 miles through the Rio Grande Valley. The Formed column keeps the build-out honest - the 1956 Federal-Aid Highway Act started the clock, the 1970s finished most mainlines, and new numbers were still being assigned into the 2020s.
Three-digit routes are the system's spare parts: belts, loops and spurs whose last digit names the parent (I-290, I-490 and I-890 all hang off I-90), and whose first digit repeats for siblings in the same city - Chicago's I-190/290/355/490 web all orbit its I-90/94 mainline. They are not in this table: the rows below are the 67 primary routes that carry the system's numbers themselves.
How to use
- Decode any number before you drive it: last digit odd = north-south, even = east-west; a 0 or 5 ending marks the transcontinental mainlines; three digits means a spur or loop, and that final digit is the parent route.
- Use the length column as a trip budget: an I-90-scale run (3,100 miles) is five driving days at interstate pace; an I-2-scale run (46 miles) is a lunch errand. The Formed column explains why some stretches feel older - they are, by decades.
- Explain the famous gaps: no I-50 or I-60 exists because US Routes 50 and 60 run through the same states and the numbering policy forbids that collision; I-99 exists only because Congress named it in 1995, breaking the sequence for a Pennsylvania corridor.
- Spot the west-coast/east-coast mirror: I-5 and US 1, I-10 and US 10, I-80 and US 30 - the Interstate grid was deliberately numbered against the older US Route grid so no number means one thing on one coast and another on the other.
Frequently asked questions
Why is there no Interstate 50 or 60?
Interstate numbering policy forbids a route that duplicates a US Route number in the same state, and US 50 and US 60 already cross the exact corridors where I-50 and I-60 would sit. The one deliberate exception proves the rule: I-99 was named by Congress in 1995, breaking the sequence for a Pennsylvania corridor - which is why the table jumps from I-97 to I-99.
What do three-digit interstate numbers mean?
They are the system's spurs, loops and beltways, and the last digit names the parent: I-290 and I-490 both connect to I-90. When the first digit repeats in one metro area, those are siblings - Chicago's I-190, I-290 and I-355 all serve its I-90/94 mainline. This table lists only the 67 primary routes with two digits or fewer.
What is the longest interstate highway?
I-90, at about 3,100 miles from Boston to Seattle - the northernmost 0-ending mainline, crossing thirteen states and using the old rail grades through the Rockies and Cascades. I-80 (2,901 miles, eleven states) and I-40 (2,557 miles) round out the three longest, while I-42 in North Carolina is the shortest at roughly ten miles.
Why do odd interstates run north-south?
The grid was designed as a mirror of the older US Routes so no number would mean one thing on one coast and another on the other: I-5 hugs the west coast where US 1 hugs the east, and I-10 runs the southern rim where US 10 ran the north. Odd = north-south, even = east-west, and the 0-and-5 endings mark the transcontinental spine - a coordinate system you can decode before you drive it.