Your cars are early American Flyer "Hummer" cars from 1918-1920. They were an inexpensive line of cars with the entire body made of one piece of folded tin. Even the "couplers" were folded-out parts of the frame. There were variations, some with "The Hummer" above the windows, others with "American Flyer". Yours have the earliest "500" lithography, it changed in later years.
The "one piece" line continued through the mid-1920's when they became part of the "Empire Express" wind-up sets, and on into the late 1920's as the "515" passenger cars. The lithography changed, but little else. They were Flyer's most inexpensive line, and the cars were very lightweight which made them ideal for the wind-up sets.
The locomotives were simple wind-ups, there was a cast iron version and a pressed tin version with a distinctive funky cow-catcher flying out front; and the early ones that came with the "Hummer" had solid wheels. There was a tiny "No. 50" tender that came with it. Google "Flyer Hummer" will bring up several images.