> Suspension bridges at a basic level only required a rope to be pulled across a river, and that can easily be done with a boat.

Or by other methods.

> Ellet's brainstorming sessions with his men raised several ideas that could enable a line to be suspended across the gorge; these included firing cannonballs with the line attached, towing it across the river with a steamer, and tying it to a rocket that would then be launched across the gorge. ... Ellet also took the opportunity to generate publicity for his project. Organizing a kite-flying contest, he offered $5[nb 6] to any boy who flew a kite across the gorge and secured the kite string to the other side.[23]

https://en.wikipedia.org/wiki/Niagara_Falls_Suspension_Bridge#Charles_Ellet_Jr.'s_temporary_bridge