In 884, Charles the Fat reunited all the Carolingian kingdoms for the last time, but he died in 888 and the empire immediately split up.
As Elizabeth is located in the Atlantic Ocean, you would have to start there. You travel down around Florida to New Orleans to then take the Mississippi River. As you travel north, you go west when you get to St. Louis, along the Missouri River.
The Yellowstone river joins the Missouri river just across the North Dakota state line.
Kingdom on Netflix is a good show thank me later