What is the difference between a US Highway and an Interstate?

Question

Aren't they pretty much the same thing?

Answer 1

A US Highway is older and can be 2, 4, or more lanes,

and have crossroads.  They are designated by white

signs with black numbers in the shape of a shield,

with the letters US on the upper part.

An Interstate highway is at least 2 lanes each way,

with onramps and offramps like a freeway,

supports higher speeds and takes more space.

The signs are red and blue shields with white lettering

saying "Interstate".

Answer 2

I-## must be limited-access.  US-## could be any old road that's part of the Federal Highway System.

Answer 3

The US numbered highways like US 1 (east Coast)  or US 101 (west coast) were  designated in 1924 with odd numbered routes going N-S and even numbered routes E-W. The numbers began in the extreme NE Corner, New England,  with US 1 south to Key West and  US2 west to Everett, WA. The Federal government pays a small part of construction costs for highways in this system

The Interstate Highway System (originally Interstate and Defense Highways) began in 1956 under the Eisenhower administration with the Federal Government paying for 90 per cent of construction costs. Once again odd numbers run N-S and even E-W, but the starting point was San Diego, thus I-5 runs north to Canada and I-8 running east. In general 3 digit numbers are either bypass routes or spurs, so major interstate highways have 1 or 2 digit numbers.

http://www.fhwa.dot.gov/infrastructure/h...