50 Fun Facts About Interstate Highway System

A stubborn urban legend says one mile in every five of Interstate must be straight to serve as what?

An emergency runway was never part of the plan: no Interstate law has ever contained such a rule, however often the story is told.

Which president signed the 1956 law that launched construction of the Interstate Highway System?

Dwight D. Eisenhower had crossed the country with an Army truck convoy in 1919, a 62-day slog that convinced him America needed better roads.

Which Interstate, running up the East Coast from Miami to Maine, crosses more states than any other?

I-95 crosses 15 states, yet until 2018 drivers had to leave it in New Jersey, where a planned stretch was never built.

On which Hawaiian island are all of the state's Interstates, including H-1, H-2 and H-3, located?

Oahu's Interstates can never cross a state line. They were built to link the island's scattered military bases, including Pearl Harbor.

Which road, nicknamed the Mother Road, was officially retired in 1985 after Interstates replaced it?

Route 66 got that nickname from John Steinbeck's novel The Grapes of Wrath, which follows Dust Bowl migrants heading west along it.

Under the Interstate numbering plan, main routes that run east to west are given what kind of number?

Even numbers mark the east–west routes, and they climb as you head north, from I-10 across the Deep South to I-94 along the northern tier.

Which country's motorway network, used by Allied armies in 1945, became a model for the Interstates?

Germany's Autobahn showed American commanders how quickly armies could move on wide, limited-access roads, a lesson they carried home after the war.

In Pixar's "Cars", the town of Radiator Springs fades after being bypassed by which Interstate?

I-40 drew the traffic away from towns like the film's. To research the story, Pixar animators drove the bypassed road in rented white Cadillacs.

Which president's wife championed the 1965 law that limited billboards and junkyards along Interstates?

Lady Bird Johnson pushed so hard for the Highway Beautification Act that it was nicknamed Lady Bird's Bill. It also paid for roadside landscaping.

The Katy Freeway, a stretch of I-10 that reaches 26 lanes counting frontage roads, is in which city?

Houston's Katy Freeway is believed to be the widest in the world after a widening finished in 2008. It was first built in the 1960s with six to eight lanes.

Which Interstate, the longest of all, crosses 13 states from the Pacific Northwest to New England?

I-90 runs more than 3,000 miles, and for about 278 of them, across Indiana and Ohio, it shares its pavement with I-80.

Which three colors appear on the standard shield that marks every Interstate route?

Red, white and blue won a 1957 design contest: Texas Highway Department employee Richard Oliver's shield beat about 100 entries, and it is now a registered trademark.

What nickname is given to the toll stretch of I-75 that crosses the Florida Everglades?

Alligator Alley began as an insult: the American Automobile Association thought the planned road would be useless to cars, a mere alley for alligators.

Which city buried its elevated stretch of I-93 in tunnels during the megaproject known as the Big Dig?

Boston's Big Dig became the most expensive highway project in the United States. A ribbon of parks, the Rose Kennedy Greenway, now covers the old route.

Which state has the most Interstate mileage, including nearly 880 miles of a single route?

Texas has more than 3,200 miles of Interstate, and its exit 880 on I-10 is the highest-numbered exit on any freeway in North America.

The phrase "inside the Beltway", shorthand for Washington politics, refers to which ring-road Interstate?

I-495, the Capital Beltway, is a 64-mile loop through the suburbs that touches the District itself only on a bridge over the Potomac.

Which tax did Congress choose in 1956 to fill the Highway Trust Fund that paid for the Interstates?

A gasoline tax of three cents a gallon fed the fund at first, so drivers paid for the new roads as they used them.

I-75 crosses which five-mile suspension span that links Michigan's Upper and Lower Peninsulas?

The Mackinac Bridge opened in 1957, ending the days when ferries were the only link across the straits. It is nicknamed the Mighty Mac.

Which Interstate is the only one to run unbroken from the Mexican border to the Canadian border?

I-5 follows the West Coast through Los Angeles, Sacramento and Seattle. Delegates from both neighboring countries attended the dedication of its final link.

Which Cold War word sits beside "Interstate" in the official name of the Interstate Highway System?

Defense reflects the network's military side: the roads are meant to speed troops between bases, airports and seaports as well as carry everyday traffic.

Which early coast-to-coast road did the Army's 1919 truck convoy follow on its two-month crossing?

The Lincoln Highway was so rough that the convoy averaged under 6 mph and broke dozens of wooden bridges along the way.

A three-digit Interstate whose first digit is odd, such as I-395, usually does what?

A spur branches off and never rejoins. Start the number with a 2, 4, 6 or 8 instead and the road is a loop or bypass that meets its parent again.

I-55 follows the Mississippi River valley north from near New Orleans to which Great Lakes city?

Chicago marks the northern end of I-55, which crosses the Mississippi River twice on its way up from the bayous.

Which Florida city marks the eastern end of I-10, the southernmost coast-to-coast Interstate?

Jacksonville ends a road that begins beside the Pacific in Santa Monica, where a sign long proclaimed it the Christopher Columbus Transcontinental Highway.

Which 1973 event led Congress to cap speeds on every Interstate at 55 mph the following year?

An oil embargo made saving fuel the goal, not safety. The national limit survived in some form until Congress repealed it in 1995.

Which state had no numeric daytime speed limit on its Interstates from 1995 to 1999?

Montana asked drivers only for a reasonable and prudent speed by day, until its Supreme Court threw the rule out as unconstitutionally vague.

Interstate traffic crosses Seattle's Lake Washington on what unusual kind of structure?

Floating bridges, among the longest of their kind, carry the road on pontoons. The original one sank in a 1990 storm and had to be rebuilt.

The highest point on the Interstate System is a Colorado tunnel on I-70 that passes beneath what?

The Continental Divide runs above the tunnel, which tops out at 11,158 feet. Trucks carrying hazardous cargo must still climb over Loveland Pass instead.

Which U.S. territory has three Interstates on paper, though none of them carries an Interstate shield?

Puerto Rico's routes, labeled PRI-1, PRI-2 and PRI-3, exist for funding purposes only and are signed with ordinary island road numbers.

Which toll road, opened in 1940 with tunnels first dug for a railroad, became a model for the Interstates?

The Pennsylvania Turnpike was the first long-distance controlled-access highway in the country. Six of its seven original tunnels had been started in the 1880s for a railroad that was never finished.

Which vice president's father, a Tennessee senator, wrote the Senate bill behind the 1956 Interstate law?

Al Gore's father, Albert Gore Sr., chaired the Senate subcommittee on roads and replaced the White House plan with a bill of his own.

A 1971 Supreme Court ruling to protect Overton Park blocked an Interstate through which city?

Memphis kept its park: the Court held that federal road money could cross parkland only when no feasible and prudent alternative existed.

Which Interstate, running from Tucson to the Mexican border at Nogales, posts its distances in kilometers?

I-19 got its metric signs around 1980, when planners assumed the whole country was about to give up the mile.

I-35 splits into east and west branches around Dallas–Fort Worth and which other pair of neighboring cities?

Minneapolis–St. Paul keeps its I-35E and I-35W even though highway officials banned new split numbers and urged states to drop the old ones.

The last major piece of the original Interstate plan, opened in 1992, runs through which Colorado landmark?

Glenwood Canyon was so narrow that engineers hung one roadway on viaducts and cantilevered the other over the river, work that won a national civil engineering award.

Which author of "The Death and Life of Great American Cities" helped stop an Interstate across Lower Manhattan?

Jane Jacobs chaired the committee that stopped the Lower Manhattan Expressway, a 10-lane elevated road planned over SoHo and Little Italy.

Which city tore down its double-deck Embarcadero Freeway, once I-480, after a 1989 earthquake?

San Francisco got its waterfront back: supervisors approved the demolition by a single vote, 6–5, and a plaza now fronts the Ferry Building.

Which of these small Eastern cities is one of only four state capitals not served by any Interstate?

Dover shares that distinction with just three other capitals: Juneau, Pierre and Jefferson City.

Which automaker sponsored Futurama, the 1939 World's Fair exhibit that sold Americans on superhighways?

General Motors hired designer Norman Bel Geddes, whose giant model of 1960 America showed motorways sweeping over mountains and through cities.

Which American general gave his name to a 1922 Army map of key roads that foreshadowed the Interstates?

John J. Pershing reported the map to Congress himself, and many of the roads it marked later became part of the Interstate network.

Which state claims the first three contracts signed under the 1956 Interstate program?

Missouri signed them on August 2, 1956, and began work on a stretch of what is now I-70 in St. Charles County eleven days later.

Which state became the first to finish its mainline Interstates, dedicating its final piece of I-80 in 1974?

Nebraska crossed the finish line 18 years after the program began; the national network was not declared complete until 1992.

The longest Interstate stretch with no services, 110 miles across the San Rafael Swell, is in which state?

Utah posts a warning sign near Green River: the next gas, food and lodging on the road are in Salina, on the far side of the desert.

I-15 threads the Virgin River Gorge, once the costliest rural Interstate per mile, in which state?

Arizona's 29 miles of I-15 are cut off from the rest of the state, and builders had to move the river's channel 12 times to fit the road in.

The Atchafalaya Basin Bridge carries I-10 over 18 miles of swamp in which Gulf Coast state?

Louisiana's twin spans run between Baton Rouge and Lafayette and rank as the second-longest bridge on the whole Interstate network.

Which state holds I-97, a main Interstate under 18 miles long that never leaves a single county?

Maryland's I-97 runs from the edge of Annapolis toward Baltimore without leaving Anne Arundel County, making it the shortest finished two-digit Interstate.

Which Interstate's out-of-sequence number was written into a 1995 law by its local congressman?

I-99 honors a streetcar: Bud Shuster named it after trolley No. 99 from his hometown, making it the first Interstate number set by law rather than by highway officials.

Which small town sends I-70 drivers through traffic lights, motels and gas stations to reach a toll road?

Breezewood is one of only two places in the country where a two-digit Interstate runs through traffic lights, and the detour can jam three roads at once.

Within each state, Interstate mile markers and exit numbers normally count up from which end?

The southern or western end is mile zero, so the numbers climb as you drive north or east. Most exits simply take the number of the nearest mile marker.

Which Idaho mining town listed its whole downtown on the National Register to block an Interstate?

Wallace won: when the freeway finally opened in 1991, it ran on a viaduct that skirts the town instead of replacing it.