With those details you provided, certainly 1931.
However initially I would go with 1991 because of its affects on the Southern districts and thus setting the stage for 1994 in states like GA, SC, AL, etc.
I'd say the mid-1960s after the one man one vote decisions such as
Reynolds v SimsA lot of states did not redistrict for the 1932 election. KY(9), MN(9). MO(13), ND(2), and VA(9) elected their entire delegations at large. CT(1), IL(2), NY(2), OH(2), OK(2), TX(3) elected their new representatives at large. All but Texas did so for the entire decade. I'd guess that they didn't bother to adjust the boundaries of the other districts as well.