The state of Texas requires that you have 2 plates. One in front and one in the rear.
Two
Texas law requires all vehicles registered in the state to have both a front and rear license plate. Furthermore, no portion of a license plate can be obstructed by anything including a license plate frame or it is violation of Texas law.
Two , one for the front and another for the rear of the vehicle .
They only require one.
There are 120 different license plates available!
IIRC, the state of Ohio requires two number plates to be displayed.
1 or 2
One on the front of the tractor, and one on the rear of the trailer.
Two
Two plates were required for automobiles and for trucks. I have a 49 F 1 Pickup that has the original license plates on it.
2 plates on tractor 1 plate on trailer