When it comes to the civil war, the Great Lakes (and Ohio) is the origin location of the>Northwest Ordinancewhich created the state-addition process. For example, it outlined phases by population milestones>PARTIAL STATEHOOD: 5,000 male settler/residents>FULL STATEHOOD: 60,000 total settler/residentsand if you really need something from the civil war itself, well, the Northwest Ordinance banned slavery (for liberty) while the so-called "Southwest Ordinance" didn't. How that impacted the expansion from Texas to California/Oregon can be debated (it removed 'subjugation' of foreign populations, but treaty citizens still happened)
Here's the path settlers took (by state addition):>East Coast>Ohio River>Great Lakes>Mississippi River>Gulf Coast (by Mississippi River and Savannah River)>West Coast w/ California Gold Rush>West Coast w/ Oregon Trail
