There are approximately 3.5 million semi truck operators in the U.S., according to Truck Info. Regional drivers can be on the road for much of the week, while over-the-road (long-haul) routes can last ...

You might notice the massive trailers pulled by semi-trucks more than the cabs in front. Look closely, however, and you'll find a peculiar little window there.

Prior to the 1930s, sleeper cabs in trucks, providing an area for drivers to rest, didn't exist. It wasn't until 1933 that Kenworth became the first manufacturer to offer an integrated sleeper section ...