Before the ratification of the 14th Amendment in 1868 each of the states had the Constitutional authority to determine the size of their legislative districts
After the 14th Amendment was added to the Constitution all of the people in every state were entitled to be equally represented which meant the size of Congressional Districts and State Legislative Districts and to be equally apportioned.
The Equal Protection Clause established the principle of "One Person, One Vote" and every legislative district in all of the states must be equal.
New Hampshire has one representative for 3.320 people and California has one representative for every 489,000 people.
This discrepancy is unacceptable, unconstitutional and unreasonable.
The Baker v Carr decision made it unlawful for the legislatures of the states to deny all of the people in their state with the equal protection of the law,
The principle of One Person One Vote prevented the legislatures of the states from creating legislative districts unequal in size. but the same standard did not apply to the apportionment in Congress.