There are minimal constraints on state legislatures’ ability to define congressional districts within their respective states. The sole provision in the United States Constitution addressing the matter of congressional districts is Article I, Section II, which states:
“Representatives and direct Taxes shall be apportioned among the several States which may be included within this Union, according to their respective Numbers, which shall be determined by adding to the whole Number of free Persons, including those bound to Service for a Term of Years, and excluding Indians not taxed, three fifths of all other Persons.
“The Number of Representatives shall not exceed one for every thirty Thousand, but each State shall have at least one Representative; . . .”
Obviously, the size of the country’s population, and its expanse, has increased considerably since the Constitution was drafted, so specifics regarding population numbers and district sizes have had to be adjusted accordingly. Basically, though, the constitution left the details of districting to the individual states.
The only other legal parameters regarding the drawing of districts is the Voting Rights Act of 1965, which was intended to prevent deliberate attempts to disenfranchise minorities through the drawing of congressional district boundaries. The process of drawing congressional district boundaries for the intent of favoring individual political parties, which was often synonymous with efforts at marginalizing minorities, goes back virtually to the beginning of the Republic. Massachusetts Governor Elbridge Gerry is credited with fathering the concept of manipulating boundaries for political advantage, giving the process its name: Gerrymandering. Gerrymandering has been a problem (or issue) ever since, right up to the present. The Voting Rights Act, however, was an effort, in the midst of the civil rights campaign, to ensure racial minorities would not be disenfranchised through such efforts by having their population concentrations used against them. The Voting Rights Act continues to be the subject of legal procedures intended to address racial issues in primarily southern states.
Political parties routinely use the practice of redistricting, which always follows the latest U.S. Census data, to try to give themselves a political advantage. The political party that controls the state house invariably attempts to “gerrymander” districts for its own advantage. By drawing congressional district boundaries in a way that ensures majority voting populations for its party, it ensures it can hold that district’s seat in Congress. Congressional redistricting will almost certainly continue to be the subject of law suits for the foreseeable future.