Population of Major US States
At the start of the 20th century New York, Pennsylvania, and Illinois where the top three US states by population. The big three southern states: California, Texas, and Florida have already all passed the old title holder states (except for Florida, but it is gaining fast).
This change shifts the momentum of the entire US down south to larger and newer states. This population shift is having and will continue to have a larger input into the US election system.