There are lots of reasons. It has to be known who can vote. There are rules determining whether you can vote or not, so it has to be made certain that you are eligible to vote. People who are not eligible cannot be registered and won't be able to vote. Election fraud can be reduced if it is known how many people can vote and what people have voted. This can stop people voting more than once or pretending to be someone else.
to be sure the voter resides at a given address which corresponds to the district the voter is voting in
Elegible and registered
There must be at least 100,000 registered voters
Delaware has 623,425 registered voters as of November 1, 2010.
There are 183,301 registered Republican voters in Delaware.
In 2012 Georgia had 5,804,812 registered voters. Of those registered voters, only 3,900,050 turned out to vote in the 2012 Presidential election.
This might help:in 2008 there were 12,752,417 registered voters in Texas.
in 2004 there were about 2,049,000 registered voters in Oregon
there are more than 250,000 registered voters (in all 50 states)
3,400,000 voters
There are 9,000,000 voters
As of September 2021, there are approximately 498,000 registered voters in Washington, D.C.
As of 2021, there are approximately 12,000 registered voters in Brooklyn, Ohio.