Answer:
The number of voting members in the US House of Representatives is fixed at 435. That was set by Congress in The Reapportionment Act of 1929.
The seats are apportioned to the states according to the population of each state, with every state getting at least one representative. Currently, seven states have only one representative. California has the most at 53.
Every 10 years the Census Bureau provides the population numbers. Some states gain representatives and some states lose representatives but the total number stays at 435.
Not included in the official count of voting members are the six nonvoting members who represent the District of Columbia, American Samoa, Guam, Northern Mariana Islands, Puerto Rico, and the US Virgin Islands (all of which are not States but federal territories which are governed by the U.S. Constitution and federal laws).