Replacing a 1950s or early 1960 solid rubber 20" bicycle tire How can I replace a '50s or early '60s 20" solid rubber bicycle tire? 

I have been looking everywhere. 

The wheel measures 17" by 1 1/2". New ones are too small to fit. 

Any information would be appreciated.
Measuring the wheel diameter will not give you the correct tire size. I suspect it is a 16 x 1 3/4 tire. I think they are still available. These tires are replaceable. You cut off the old one with a hacksaw. Mount the new tire by first soaking it in hot water for about 20 minutes. The heat will make it larger in diameter and more pliable. Work it on the wheel with your hands and if needed careful use of a screwdriver. I rubber mallet will help seat it.