West virginia constitution
Article VI: the legislature
Section 10

The arrangement of the senatorial and delegate districts, and apportionment of delegates, shall hereafter be declared by law, as soon as possible after each succeeding census, taken by authority of the United States. When so declared they shall apply to the first general election for members of the Legislature, to be thereafter held, and shall continue in force unchanged, until such districts shall be altered, and delegates apportioned, under the succeeding census.