This is the Upper Niagara River. The maximum width of the river is 8500 feet at Buffalo/Fort Erie and it narrows to about 1500 feet at Squaw Island below the Peace Bridge, in Buffalo. What is strange, is that researching the widest river in the US and the world, there were so many claiming to be the widest. I could not get a consensus on just one answer for each, but the Niagara River is nowhere near the widest. When you see the image above, it does look like a lake instead.
The view above and below is looking at the Grand Island Bridge to the largest island in the Niagara River at 27 square miles. The largest island in the world appears to be Greenland at 822,706 square miles. I lived on Grand Island when I first moved to New York.
The 35 mile long river is not actually a river because it connects two bodies of water and it is often referred to as a strait. It connects Lake Erie and Lake Ontario, flowing north. Many different professions have been interested in The Niagara River, from geologists, artists, historians, archaeologists, botanists, mechanics, and electricians.
The longest river in the world is not too surprising. It is the Nile at around 4,160 miles. I say about because it appears no one can agree on this either. And oddly enough, they can not agree on the length of the short Niagara River either. Some had it listed at 22 miles long and these came from sources that should actually know.
This photo below, is one of the water intakes that are used to divert water for hydro-electric generating.