In the 1988 column entitled, “How can there be interstate highways… in Hawaii?”, Cecil says there are no interstate highways in Alaska.
According to the website of the Federal Highway Administration, there are four designated interstate highways in Alaska, comprising 1082 miles of roadway.
Also, Alaska’s interstate highways are not signed as interstate highways and have state numbers that do not match the federal interstate highway system.
Interestingly enough, Puerto Rico, another island, has four interstate highways.
Another Interstate Highway that isn’t actually “interstate” is the Tri-State Tollway, which isn’t “Tri-State” at all. Going north to south, it begins at Northbrook, Illinois and ends just past South Holland, Illinois, just short of the Indiana border.
Thus the reason for Alaska having “Interstate Highways” is funding: the federal government has a separate pool of money to fund these highways and pays a higher percent of costs (vs state governments) than for other highways.
But were they there in 1988, when Cecil wrote his column?
Though, the Tri-State (I-294) is a classic example of the concept of an “Auxiliary Interstate Highway.” They usually have a three-digit number, and the last two digits are the number of their “parent” Interstate. In the case of the Tri-State, it’s a “loop route,” and bypasses the center of Chicago, connecting up with its parent, I-94, to the north and to the south of the city (whereas I-94 goes through the center of the city).
Many (maybe even most) auxiliary Interstates only run in a single state.
I don’t think all “interstate” highways outside of Alaska and Hawaii are necessarily interstate. Does I-4 run anywhere outside of Florida?
I’ve been doing some research, and it’s very probable that funding has more to do with it than whether or not the highway spans more than one state. If you can get an Interstate highway built in Hawaii, the Federal Government provides most of the money through the National System of Interstate Highways special funding, thus saving the state a very large sum of money.
In the one or two digit category there are quite a few that are one-state only. I-2 in Texas is the lower numbered one. Search this page for “only”. (My count is 20. YMMV.)
Those Alaskan Interstate Highways do in fact appear to lead to the Canadian border and the rest of the United States, thus making them legitimate interstate highways, as opposed to some of the obviously fake “interstate” highways noted above.
I-96 also starts and ends in Michigan, going from Detroit to Lansing to Grand Rapids to Muskegon, which is at the shore of Lake Michigan.
It’s on the “only” list I linked to above. It’s the 2nd highest single state one listed. (Reminder: 1 or 2 digits.) I-97 in MD is the highest.
It would be interesting if there was a 1/2 digit interstate that started and stopped in the same state but passed thru another state. But that doesn’t appear to be the case.
Guess which state has the longest “only” interstate?
New York! Texas is in 2nd place by a good margin.
I believe the Interstate system was also conceived to be part of a civil defense plan, plus suitable for military use.
Yes. Among other things, the maximum grade is 6%* and the minimum clearance of underpasses is 16 feet, the height of a main battle tank atop a transporter.
*With a few exceptions
I can think of two of these in Texas. One, I69, has bits and pieces in other states, but none of them cross state borders to my knowledge. The other is I45, which runs from Galveston to Dallas, then just starts being a state highway up into Oklahoma.
The list I linked to earlier lists 5 Texas only 1/2 digit interstates.
As to I-69, the original segment from Indianapolis to Port Huron crosses a state line as well as two other state line crossings.
