The Mexican Revolution and the Louisiana Purchase opened the West to further expansion
The Mexican-American War that ended in 1848 added 1 million square miles to US territory, enabling thousands to enter California and other parts of the west.
A different kind of revolution - the revolution of agriculture - also impacted westward growth. Because of the grasshopper - sod-cutting plow - poor settlers and homesteaders were able to move West, knowing they'd be able to build their own home. There were several ways a homestead of nearly free land could be acquired; most demanded that the head of the household live on the land.
Incidentally, Native Americans had homes dug out of the earth they called 'earth lodges.' These Navajo people - the father a silversmith - are outdoors, with their earth lodge.
When we moved from Texas to our Oklahoma cattle ranch, my father saw all the evidence of pigs. Immediately he started to fence the place, three strands of barbed wire at the top and hog netting below. It was costly, labor-hungry work, but it was possible. Until 1873, it wasn’t.