Congressional Districts. For every 1 Congressional District there is 1 corresponding Member of the House of Representatives. Explore the map here: https://mapchart.net/usa-congressional-districts.html
Something we have to foresee is “Congressional Redistricting”. This will next occur in 2021. There are many things that have to happen before that time.
One of those things is the US Census, which in 2020 plans to either ask or “not ask” the question “Are you a US Citizen”. There is precedence for asking the question, and the 3/14/2019 Oversight Committee Hearing reminded us that in 2000 the US Census by Bill Clinton asked the question. Was Bill Clinton including the question w/nefarious purposes in mind? Dept. of Commerce Secretary Wilbur Ross did not think so, in his testimony.