THE CONSTITUTION

Article I

Section 2. The House of Representatives shall be composed of Members chosen every second Year by the People of the several States, and the Electors in each State shall have the Qualifications requisite for Electors of the most numerous Branch of the State Legislature.

No Person shall be a Representative who shall not have attained to the Age of twenty five Years, and been seven Years a Citizen of the United States, and who shall not, when elected, be an Inhabitant of that State in which he shall be chosen.

Notice here that the qualifications to be an elector are left up to the individual state.

[clause here omitted which was changed by the 14th amendment]
The actual Enumeration shall be made within three Years after the first Meeting of the Congress of the United States, and within every subsequent Term of ten Years, in such Manner as they shall by Law direct. The number of Representatives shall not exceed one for every thirty Thousand, but each State shall have at Least one Representative; and until such enumeration shall be made, the State of New Hampshire shall be entitled to chuse three, Massachusetts eight, Rhode-Island and Providence Plantations one, Connecticut five, New York six, New Jersey four, Pennsylvania eight, Delaware one, Maryland six, Virginia ten, North Carolina five, South Carolina five and Georgia three.

This clause set up our need for a census every ten years. The census was to be used to determine the number of representatives in the House. Since they could only guess how many people lived in each state at the time, they arbitrarily chose the numbers of representatives given above as a starting point.

When vacancies happen in the Representation from any State, the Executive Authority thereof shall issue Writs of Election to fill such Vacancies.
The House of Representatives shall chuse their Speaker and other Officers; and shall have the sole Power of Impeachment.

This gives the state government authority to replace representatives who have died or otherwise resigned in office. Very importantly, the House of Representatives was given the sole power to impeach (question) and investigate allegations of wrongdoing by all others in federal office. If they determine by simple vote that an impeachable offense has occurred, they would turn the subject over to the Senate for trial.
:)