On January 1, 1927, “Final location of the United States’ most important roads in the country was announced today by the bureau of public roads of the department of agriculture. The system as finally selected embraces ten main transcontinental routes designated by numbers which are multiples of ten while the important north and south routes are numbers 1, 11, 21, etc.”
Thus reported the Chicago Tribune on January 2, 1927. The original numbering scheme for what we now call the U.S. Highway System had been finalized in November 1926, but the public announcement of the route system was delayed until the New Year of ‘27.
Here is the rest of the article from page 23 of the 01/02/1927 Trib, which was headlined “U.S. Marks Ten Main Roads With Route Numbers”:
Virtually all the large cities of the nation are served either by the through routes or connecting roads.
The route numbering system which has been decided upon will be of great assistance to tourists in following through routes. All east and west routes bear even numbers, while north and south routes have odd numbers. Frequently three digit numbers are used to indicate branches of through routes. For example route 40 is a direct road.
Convenience of Travelers
There will be no difficulty in following any selected route since a standard sign showing the route number has been adopted and also standard danger, caution and directional signs. These standard signs will add greatly to the safety and convenience of travel as there will be no change in their character in passing from one state to another.
Twenty-two states already report their United States highways completely marked, fourteen report the work partially complete and six which have not yet started anticipate that it will be completed next season.
Push Work Rapidly
The system in its final form has the approval of each of the state highway departments and work on the unimproved sections is to be pushed rapidly.
No special funds are to become available as the result of the designation of any road as a part of the system. The purpose has been to select a main system of highways for the nation, the unimproved sections of which will be given priority in improvement, and to eliminate confusion as to route designation, marking, and safety signs. Virtually all of the system is on the system of federal aid highways and is eligible to receive federal aid.
End of article.
A couple of thoughts:
The Article notes 22 states with U.S. highways markings complete, 14 with partial completion, and 6 that expected to be done in the 1927 construction season. That was 42 of the 48 states. Illinois was NOT one of those 42–research by myself and Carl Johnson shows that our state did not put up U.S. Highway markers until the summer of 1928. Here is a map from the 1927 Rand McNally atlas showing the U.S. Highways in the Chicago area, even though the route markers would not be posted until 1928.
This article crystalizes something that still seems to be misunderstood by many–that the U.S. Highway system had “no special funds.” The purpose then as always was to “eliminate confusion as to route designation, marking, and safety signs.” The unimproved portions of road that were designated as U.S. Highways were to be given priority of improvement, nothing more. That most of the highways designated as part of the U.S. system would be eligible for federal aid was coincidental.
So, what “confusion” were they eliminating? There were two systems in place back in 1927–state highways and named auto trails. State highways then as now were marked to state lines, where the system of the neighboring state would take over. The only systems that were consistent across state lines were the marked auto trails–such as the Lincoln Highway, the Yellowstone Trail, the Lone Star Route, and the Dixie Highway. The quality of marking depended upon the degree of competence of the particular highway associations, and often the traveler was left with no reliable information in the middle of nowhere.
Thus, the announcement that the several states would cooperate on a system which would be consistently numbered across state lines was greeted with approval with everyone EXCEPT some of the auto trail associations, who knew that the U.S. system would lead to the extinction of the named trails.
Although some of the named trails had been well-maintained (such as the Lincoln Highway), the advent of the U.S. system was indeed a step forward, an improvement that was a true boon to the auto traveler.
Today is a special day. One of my personal areas of interest since becoming involved with the historic highways of Chicago and the U.S. has been a little filling station located at 3801 W. Ogden Avenue on the city’s west side. (I have a story about the station on my website here.) Built in 1925 and operated by John J. Murphy for over 40 years, the building is often referred to as the Castle Car Wash. This is the name painted on the front—likely the last entity to attempt to use the building for commercial purposes. The building has been sitting vacant and deteriorating for the last 20 years or so. Subject to benign neglect during the long economic decay of the surrounding North Lawndale neighborhood, new commercial and residential improvements in the area puts new pressure on the historic structure’s survival. Today, Landmarks Illinois drew needed attention toward the Murphy Filling Station when they placed it on their 2009 Chicagoland Watch List of endangered historic structures. In operation for more than 30 years, Landmarks Illinois has saved countless architectural and historic treasures throughout the state of Illinois. For more information about Landmarks Illinois and the Chicagoland Watch List, visit http://www.Landmarks.org. The Watch List includes many structures, all worthy of preservation. Landmarks Illinois is also highlighting the importance of neon signs, another part of our commercial landscape that is disappearing. To see the entire watch list, click here. 
I recently received my copy of the Spring 2008 Route 66 Magazine. The cover story on the public art of Joliet, Illinois is great, since it showcases the great work that has been going on in that city over the last several years.
I have not yet seen the exhibit nor read the book, but the Tribune article has this excerpt from the book’s essay by James R. Ackerman: