"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 6 runs through 14 states, so that leaves lots of room for error. And I suspect there have actually been numerous errors in the past, which might explain why one can find many different figures for the length of US 6. Back when the route still went all the way to Long Beach, an oft-cited figure was 3652 miles. For example, that was the distance used on both a 1953 plaque in Long Beach and on a sign fairly-recently posted in Provincetown:
However, signs that were posted in Provincetown during that actual timeframe gave at least two different figures which were similar to each other but significantly less than 3652:
Kind of interesting to note the "route" illustrated for highway 6 was not very accurate, especially in the West, where it looks like the terminus was in the Bay Area rather than Long Beach. Anyway, was the town of Friend really the midpoint of US 6? From my calculations, it was actually pretty close. The true midpoint was about 12 miles west of Friend, somewhere between the towns of Exeter and Fairmont.
That truncation shifted the midpoint of US 6 by 125 miles, and by my calculations it is now located not far from Oakland IA. Then in 2019, Iowa DOT rerouted US 6 traffic in Council Bluffs, increasing the length by exactly three miles. So as of 2020 the total distance is 3212 miles.