Final answer:
Settlers traveling to Oregon crossed the Oregon Trail, which went through the Rocky Mountains and into the Willamette Valley, while those heading to California diverged southward onto the California Trail.
Step-by-step explanation:
Settlers heading to Oregon's Pacific coast had to cross the Oregon Trail, which spanned across plains and through the Rocky Mountains, ending in Oregon’s Willamette Valley. Those seeking to reach California's Pacific coast traveled similar routes but then followed the California Trail as it branched southward from the Oregon Trail into California.
During the westward expansion, the Oregon Trail began in places like Independence, Missouri and was a key path for settlers driven by 'Oregon Fever' and the desire for new land and economic opportunities. Despite the hazardous journey that included disease, accidents, and unfamiliar terrain, this large-scale migration was integral to the American pioneer spirit and the Manifest Destiny ethos.