Until 1910, As The US Population Grew, More Electable Seats Were Added To The US House Of Representatives: The House Grew From 65 Initial Members To 435 Members

From The New York Times, Economix, "Enlarging the House of Representatives" by Bruce Bartlett:

The Constitution is silent on the question of whether the House would increase in size as the population of the United States grew. James Madison was among those with concerns that the House would not increase in size, leading to increasingly large districts, which he expressed in Federalist 55.***Madison’s fears proved unfounded for more than 100 years. The size of the House was increased with additional states and rising population from 65 members in the first Congress to 435 after the 1910 census.

But after the 1920 census, Congress failed either to increase the size of the House or change its apportionment, despite the fact that the population had both substantially increased and changed its geographical distribution significantly.***Eventually, President Herbert Hoover pressured Congress not only to resolve the apportionment standoff, but to do so permanently. This led to passage of the Permanent Apportionment Act of 1929. Not only did it permanently fix the size of the House at 435, but it established a mathematical formula for automatic reapportionment after future decennial censuses.***[T]he House of Representatives is on the very high side of population per representative at 729,000. The population per member in the lower house of other major countries is considerably smaller: Britain and Italy, 97,000; Canada and France, 114,000; Germany, 135,000; Australia, 147,000; and Japan, 265,000.