This is the original pre-1937 Route 66, east of Amarillo TX. An 18-mile stretch without pavement was known as "The Jericho Gap." It was merely hot and dusty most of the time, but after a thunderstorm this section of 66 turned into impassable gumbo.

Locals made extra money pulling Dust Bowl refugees out of the mud. (There's lots of irony in that, although the refugees failed to notice it.)

This 21st Century view shows the very same mud after a thunderstorm. This is now a county road and hasn't changed a bit since the 1930s. The field at left, filled with water, is actually higher than the roadway. It should of course be the other way around.

At least two vehicles, presumably trucks with 4-wheel drive, have made it through. My tripod was set-up a couple of feet from this mudbowl. The road there was dry.