A detail from the I-74 Feasibility Study Area Map. Courtesy of N.C. DOT.
The numbering of the Interstate highway system came about as the result of the Federal-Aid Highway Act of 1956. The actual numbering was done by the American Association of State Highway Officials (AASHO) based on a numbering plan devised earlier for the U.S. Highway System.
In the Interstate numbering scheme, east-west highways are assigned even numbers, as is I-74, while north-south highways are assigned odd numbers, such as I-95. Odd route numbers increase from west to east, as you can see by looking at a U.S. road atlas, with I-5 running from Canada to Mexico along the West Coast, and I-95 running from Canada to Miami on the East Coast.
Correspondingly, major east-west interstates increase in number starting from the south with I-10 between Santa Monica, CA, and Jacksonville, FL, and going north to I-90 running from Seattle, WA, to Boston, MA.
There is no special significance to the numbering of I-74, other than it it is located relatively in the center of the country and follows the original numbering scheme set by AASHO.
The primary routing of I-74 is between the Quad Cities in Iowa, and Cincinnati, Ohio, a length of 348 miles. Approximately 80 miles of disconnected I-74 exist in North Carolina. Construction of the Midwest section of I-74 began in 1958 in Davenport, IA, and was completed at its Cincinnati, OH, end in 1974, according to the Iowa Department of Transportation.
While the original plan envisioned I-74 extending from Cincinnati through West Virginia and Virginia before connecting to the North Carolina section, no firm plans have been developed and no money has been budgeted for construction.
Today the interstate numbering system is maintained by the Federal Highway Administration (FHWA).
RELATED LINKS:
How far in the future is the Future Interstate 74 Corridor?
Why is the DOT digging holes on 74/76 between Leland and Riegelwood?
Website for the National I-73/I-74/I-75 Corridor Association
Date posted: March 18, 2013
User-contributed question by:
Don Jackson
IIRC, US-74 has some I-74 signs (I don’t recall if any of US-74 is up to interstate standards nor whether any of US-74 is – in fact – US-74 & I-74) between I-95 and Leland. This link – after googling I-74 – http://en.wikipedia.org/wiki/Interstate_74 does include some info on I-74 in N.C.
Some of them say “Future I-74 Corridor.” I remember passing one when I was behind a beat-up old Ford Galaxie going 40 mph on that old two-lane stretch of U.S. 74 just west of I-95, before the interstate-style freeway was built to Laurinburg. I found the sign very ironic!