Independence, Missouri was founded in 1827. It is located where the Missouri and Mississippi rivers meet. Started as a trading post and flourished into a town. It is a common place for pioneers to stock their wagons before heading west.
Another starting place could of been St. Louis
Oregon City, Oregon was founded in 1842. It is located where the Willamette river meets the Columbia river. Was and still is a place where trade is popular between native americans and white people. The river supplies power to mills helping its economic development.