@Elderberry@mystery-ak Here is when and why and how lines are drawn in Texas:
They are re-drawn after every nation wide census.
They are re-drawn because population grows and people move from one place to another.
This is how they are drawn according to laws on the books how to do it:
County:There is a limit to the number of people who can be in a county precint. After the national census, if a precinct has too many people in it, a new precinct must be drawn, bringing down the number in the over populated precinct to the accepted amount. The County Commissioners' court has the responsibility to re-draw the lines.
State:There is a limit to the number of people who can be in a state voting district. After the national census, if a district has too many people in it, a new district line must be drawn, bringing down the number in the over populated district to the accepted number in it.
The Lt. Governor has the responsibility for appointing a committee to re-draw the lines. The Lt. Governor in Texas is a Republican, so he appoints Republicans to be on the committee. He can choose whomever he wants. After one census, I had two friends who were on this committee and they kept me advised as they went through the process. This is not quickly done. The lines are drawn as much as they can be so the district is connected throughout - one solid piece of land, not a bit here, skipping over another area, picking a bit here and skipping over to another area, picking a bit there. If that happens, it means it is a gerrymandered district - choosing who is in it based on voting, rather than just numbers of people.
There is one gerrymandered district in the Houston area. It was done on pupose a number of years ago. It looks like a puzzle piece, bits chosen here and there. That was done to create a black voting district - Sheila Jackson Lee has been the Representative since it was created.
Texas Democat Legislators have complained for years because Republicans have drawn the lines. One year, a number of Democrats left the state, went into New Mexico and Oklahoma so they wouldn't be there and lines could not be voted on. Texas Rangers were used to get them back into the state.