US 50 is one of the longest highways in the U.S. How long is it? Well, there's actually some debate on that (this page has more details about why that is).
Both the Maryland and California state departments of transportation have placed reciprocal mileage signs at the terminus points, each claiming the total distance is 3073 miles. This photo was taken in Ocean City MD, looking along the east beginning of US 50...
Many Route 66 tourists simply enjoy the romance and the lore of the fabled road. The facts aren't all that important, and if one of the legends turns out to be a tall-tale, they'd rather not know about it. And that's fine -- if you're one of those people, I say you gotta do you -- get out there and enjoy the Mother Road.
...then you might want to stop reading here, because this page contains research that discredits some of the "conventional wisdom" about US 66 that is found elsewhere. On the other hand, if you're interested in facts and details, then please carry on.
(last updated 3/4/2020)
Why it is difficult to obtain accurate end-to-end mileage for many US highways
This comes as a surprise to some, but US highways are actually not federal highways... at least not in the sense that they are owned and maintained by the federal government. Rather, the US routes are actually just state highways... although they are "special" in the sense that at some point they were granted permission by AASHO (later AASHTO) to be signposted with a US route shield.
"One great red line"
For about a quarter-century, US Route 6 was the longest highway in the country. In Jack Kerouac's novel On the Road, the main character described it as "one great red line across America". During those years it ran between Provincetown MA and Long Beach CA, and I believe there has never been a longer highway in the United States. Exactly how long was it? Well, believe it or not, the answer to that question is debatable (see this page for more details about why it is difficult to calculate).
US 264, US 501, US 27, US 104, US 441, Apalachicola, Intra-state routes, Wrong-way overlaps, US 164[i], US 121[i], US 221, Joplin, US 202, US 641, US 136, US 34, US 48 [ii], US 36, US 21, US 219, US 220, Keokuk, Colors, US 171, New Orleans, Jacksonville, US 68, US 150, Philadelphia, US 64, US 11, Erie, Waverly, US 14, US 77, US 83, US 212, US 216, US 385. US 73, US 169
In 1979 Arizona asked AASHTO to extend the US 93 designation to Phoenix; following is the route description from the actual meeting minutes:
By 1970, US 666 had reached its maximum historical extent, from Douglas AZ to Monticello UT (represented by the blue line on this map):
Just outside the north edge of Great Smoky Mountains National Park is a scenic Tennessee highway connecting I-40 near Newport to Gatlinburg and Maryville. During the late 1970s and early 1980s, it appears TNDoT was determined to unify this corridor with a single US route designation. They first attempted to accomplish this by extending the US 74 designation west from Asheville NC (which was the route's western terminus from 1926-1987). Following is the route description from the actual minutes of the June 1978 meeting of AASHTO's route numbering committee:
In 1967 the US 270 designation was at its maximum extent, from Pine Bluff AR to Syracuse KS. That year the Kansas DOT petitioned AASHO* to extend the US 270 designation even further: