One of the original unratified Amenments to the constitution (that has no deadline for ratification btw) would have capped Congressional districts at 50,000 people per district, or around 6,660 seats in Congress.
t e c h n i c a l l y the amendment as written would have no effect because of a last minute change in the original wording. but they can just repeal the reapportionment act of 1929
If this amendment were law, individual municipalities down to Elkhart, Indiana would have their own House district. Districts that small would also mean that you'd probably be able to reach your Representative much more easily, you might even know them personally.