The US Highway numbers are the primary means of organizing routes. The numbered US highway system was adopted during the 1920's, as automobiles became more affordable and more roads became paved. Odd numbered highways generally would run north and south, with higher numbers to the west. And even numbered highways generally would run east and west, with higher numbers to the south. Three digit highways are usually variations or branches of the highways with those last two digits. One exception is US 101, along the Pacific Coast, which really is part of the two digit numbering system.

Each Greyhound or Trailways route segment listed might include the following data.

US Highway Number
Following routes using US Highways are routes using state ("S") highways or other roads. For the Midwestern states, separate pages cover bus routes over state highways. Additional abbreviations used are "C" for route segments in Canada, and "T" for "turnpike", which were the earliest limited access highways, later evolving to the Interstate highway system. Also used is "I", for the interurban railways which were the predecessors for a few intercity bus routes.

Russell's Guide Table
Schedule table numbers, from the June 2005 Greyhound System Timetable, and from the January 1976 Russell's Official National Motor Coach Guide. Since 1927, Russell's Guides has been publishing the monthly Guide containing all the schedules of the various bus companies operating throughout North America.

Greyhound Or Trailways Company Or Division
Abbreviation of the Greyhound or Trailways company or division which eventually operated the route. Although all Greyhound companies later became part of a single Greyhound Lines company, while most Trailways companies later became part of Continental Trailways.

Year Introduced
Wherever possible, the first known bus service over each segment is included. In some situations, there were differences in whether service was local or through, or intrastate or interstate. Generally these details are not covered. Until 1935, interstate bus service was not subject to regulatory authority at the federal level, while many states began regulating intrastate service in earlier years. Also, situations existed where if one bus company already was operating over a route segment, a new bus company using the same route segment would be prohibited from carrying local passengers. As a result, sometimes a Greyhound or Trailways company would introduce a new long route, but originally only permitted to transport long distance or interstate passengers. The Greyhound or Trailways company might later acquire existing local bus companies operating over same route, in order to gain the local or intrastate rights held by the existing companies. Also, a new bus company would typically be prohibited from carrying local passengers within a city, where a streetcar or local bus service already existed.

Original Company
First known company to operate bus service over route, if a smaller company which later became part of Greyhound or Trailways. Dashes indicate if service was originally introduced by a larger company, abbreviated to the right.

Year Consolidated/Consolidated Company
Indicates when a route was introduced or acquired by a larger company, indicated as an abbreviation. When abbreviation is different from "Greyhound Or Trailways Company Or Division" abbreviation, indicates an intermediate company which was later acquired by a Greyhound or Trailways company. History of consolidation into Greyhound or Trailways companies mentioned below routes list for each page.

The Russell's Guides dated February 1948 and January 1976 were the original major resources used, to determine the existence of routes during various eras. And additional issues of the Russell's Guide were subsequently used for later research. Routes listed generally were in existence in 1948.

Routes existing in 1976 are identified with the table numbers from that Russell's Guide. And a Russell's Guide from August 1971 was later used, to add table numbers for routes discontinued between 1971 and 1976. From 1970 to 1987, there was stability in the numbering of the Russell's Guide tables. The tables were renumbered to the present scheme in 1987, with Greyhound's acquisition of Continental Trailways. And during a period when Greyhound system timetables could be ordered by mail, a June 2005 timetable was used for those table numbers. Those Greyhound timetables basically resembled the Russell's Guide.

As of the 1970's, a nationwide route network was in place, which was mostly stable due to regulation. In these listings, where a table number space is blank, route had been discontinued by then. 1976 was only a few years before deregulation of the industry would result in elimination of local stops and discontinuance of many branch routes. Only a few major routes remain. And where Interstate highways have been constructed through the corridors originally served by the US Highways, buses now generally use the Interstate highways, exiting only to serve the largest towns.

Also mentioned are independent bus companies which had operated over various US Highways. The continued existence of such companies into the 1970's and later are indicated by the presence of Russell's Guide table numbers. The company in existence in 1948 is mentioned, except when part of a larger company by 1956, in which case the larger company is mentioned. Where two companies are separated by a slash ("/"), a different company was operating the route in 1976, mentioned following the slash.