The U.S. Constitution allots for 1 representative in the house per 30,000 citizens, and 2 senators per state, 'reapportionment' tied to evaluation of the census. HOWEVER, while the number of senators has kept, the membership of the house has been frozen at 435 (save for temporarily 437 with the admission of Alaska and Hawaii) since 1913, amidst an almost completely different time.
In 1913, there were barely any household telephones, and very few people had personal automobiles. There are now over a billion cars on the planet, and we are connected by the internet, which is accessible even in our eyeglasses, pocket phones, and watches.
Currently, 1 member of the house wields the effective voice of 700,000 constituents, and 1 senator wields for millions. Expansion = Better Representation.