Complex sentence: Utica is located at the shallowest spot along the Mohawk River which made it the best place for fording across, and an Iroquois Indian crossroads and fording location made trade exceedingly easy for local merchants.
Split into simpler sentences: Utica is located where it is because it was next to the shallowest spot along the Mohawk River which made it the best place for fording across. Also due to an Iroquois Indian crossroads and fording location it made trade exceedingly easy for local merchants.