Not too difficult. The wagons crossed at shallow places and they used ferry's to cross deeper waters.
The Mormon trail crosses several rivers. Probably the most well known would be the Sweetwater River near Martin's Cove in Wyoming.
It was a difficult trek, and many died along the trail.
Montana
Nebraska
A scow was used cross the rivers.
The first Mormon Pioneer group took 2 years to cross the Mormon trail... this is mostly because there wasn't yet a trail and they didn't really know exactly where they were going. Later groups took several weeks to several months, depending on the number of people, weather, and mode of transportation.
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The Mormon Trail began in 1847.
The Mormon Trail started in February 1846.
Mormon Trail was created on 1978-11-10.