Toll roads (and bridges) are authorized, built and run at the state level. Sometimes it's a state department that builds them, but often its a quasi-state agency or even private consortium. Construction is usually paid for with bonds, which are repaid from revenues. In theory, if not in practice, tolls on one road will free up gas tax money for use on other roads. Details can vary with state and the authorizing legislation.
Especially in the east and parts of the midwest, toll roads were built (or at least started) before the interstate system was funded. But even in wild west there were privately built toll wagon roads over some of the passes. Most newer toll roads are supposed to add capacity and speed in and around growing metro areas.
https wrote:
A short list of Idaho toll roads and ferries built by private funding includes Boise to Idaho City Toll Road 1864, Fairfield to Rocky Bar Toll Road 1864, Challis to Bonanza Toll Road 1879, Walter's Toll Ferry 1863, Salmon Falls Toll Ferry 1863 and Idaho Falls Toll Ferry 1864.
EZPass is a 19 state toll reciprocity program.
https://www.e-zpassiag.com/about-us/membersMost of my memories of tolls are from the 80s and earlier in Chicago and points east. Then we paid by tossing coins in a hopper, or cash with an in/out ticket. I haven't had need to use the automated tolls on Seattle area roads.
But for all practical purposes ferry fares are tolls.