Interstate 55 (I-55): Route, Mileage, History and Crash Data

How long is I-55?

Wikipedia and Interstate Guide both put I-55 at 964.25 miles end to end. The FHWA Route Log, as of January 2026, credits it with 940.06. The two figures differ mainly because the Route Log books some pavement that I-55 shares with other Interstates to those routes instead.

Illinois accounts for most of the gap. Its Route Log row reads 294.38 miles, while Interstate Guide lists 313.08 for the state. The 18.70-mile difference matches the 16.00 miles I-55 shares with I-70 east of St. Louis plus the 2.7 miles it shares with I-64, both noted in the Route Log. Smaller shared stretches account for most of the rest: 1.60 miles with I-20 in Jackson, 2.22 with I-40 in West Memphis and 1.00 with I-44 in St. Louis. Tennessee carries the fewest miles, 12.35 through Memphis.

Where I-55 starts and ends

The southern end is at I-10 in LaPlace, Louisiana. The northern end is at US 41 near McCormick Place in Chicago.

Going north, I-55 passes Hammond, Jackson and Hernando, then crosses Memphis and the Mississippi River into West Memphis, Arkansas. After Sikeston and Cape Girardeau in Missouri, it crosses back to the east bank at St. Louis. In Illinois it serves Springfield, Bloomington-Normal and Joliet before reaching Chicago on the Stevenson Expressway.

Interstate junctions along I-55

The list follows I-55 from south to north, starting with I-10 and I-12 in Louisiana and ending with I-90 and I-94 on the Dan Ryan in Chicago. I-64 shows up twice, once in Missouri and once in Illinois. Arkansas contributes only I-40, and the short Tennessee stretch adds no main-route entry. Illinois has the longest run, eight entries from I-64 and I-70 at East St. Louis to I-90 and I-94 in Chicago.

Fatal crashes on I-55

Fatal crashes on I-55 killed 477 people from 2020 to 2024, in 423 crashes, or about 95 deaths a year. The route's rate is 9.9 deaths per 100 route miles per year, a bit above the Interstate average of 9.5, and it ranks 20th of 56 routes, counting from the highest rate.

Mississippi had 164 deaths and the highest state rate on the route, 11.3. Illinois followed with 154 deaths and a rate of 9.8. Arkansas had the lowest rate, 7.5. Tennessee's 16 deaths fall on too few miles to give a state rate. Cook County had the most deaths of any county with 37, ahead of Hinds County, Mississippi, with 36 and Will County with 32. Deaths rose from 82 in 2020 to 103 in 2024, and 2022 was the only year that fell.

Counties with the most I-55 crash deaths

Bridges on I-55

The 2025 National Bridge Inventory counts 835 bridges on the I-55 main line, and 21 of them, 2.5 percent, rate Poor. Illinois has 17 of those 21, 7.2 percent of its 237 bridges on the route. Mississippi has the most bridges, 302, with 2 rated Poor. Half the bridges on I-55 date from 1965 or earlier.

In Louisiana, I-55 crosses the Manchac Swamp on a causeway of nearly 23 miles. At Memphis it crosses the Mississippi on the Memphis-Arkansas Bridge, a 1949 cantilever truss with no shoulders that Interstate Guide says falls short of modern Interstate standards. It is the only Interstate bridge in Tennessee on the National Register of Historic Places.

Tolls on I-55

I-55 has no entries in FHWA's January 2023 toll inventory. Neither Wikipedia nor Interstate Guide describes toll or express lanes opened on it since, so a trip from LaPlace to Chicago pays no tolls on I-55 itself.

I-55 auxiliary routes

Four three-digit numbers come from I-55, and I-155 is two separate roads. One runs about 32 miles in Illinois between Lincoln and Peoria. The other crosses from Missouri near Caruthersville over the Mississippi to Dyersburg, Tennessee. I-255 covers about 31 miles of the St. Louis area in Missouri and Illinois, I-355 runs through Chicago's western suburbs by way of Bolingbrook, Downers Grove and Lombard, and I-555 heads from I-55 in Arkansas to Jonesboro.

How I-55 was built

I-55 was laid out under the Federal-Aid Highway Act of 1956. Mississippi's first approved segment, 27 miles through Hernando, Coldwater and Senatobia, broke ground at Coldwater in July 1957. In Missouri, the section from north of New Madrid to Sikeston opened on September 1, 1960.

Between St. Louis and Chicago, I-55 replaced US 66, and much of its Illinois route follows the 1940 alignment of the old highway. Chicago's Southwest Expressway opened on September 1, 1964 and took the Adlai E. Stevenson name a year later. The last Chicago piece, east to US 41, opened in 1966. St. Louis had its section done by 1967, Mississippi closed its last gap between Canton and Vaiden in 1973, and the full route was finished in 1979. In July 2018 the stretch from I-294 to near Pontiac became the Barack Obama Presidential Expressway.

I-55 traffic and road conditions

Searches for I-55 lean toward today's crashes, winter closures and work zones. The six states along the route each run a traveler website for that, linked below in order from Louisiana north to Illinois.

I-55 questions