Click on image for Texanic-sized map.
The Texas House of Representatives has 150 representatives which are apportioned among the counties based on population. The Texas constititution provides that a single county may have multiple representatives; or multiple contigious counties may be joined together into a single district with one representative.
But the Constitution also provides that counties entitled to more than one district, may be joined to adjacent counties for the purposes of apportioning representation for their surplus population beyond that needed for a whole number or representatives. For example if two neighboring counties had a population equivalent to 2.5 and 1.5 representatives, one county could elect 2 representatives, the other 1 representative, and the voters of the two counties together could elect a 4th representative. Such a shared district is called a
floterial district. Since the two counties were entitled to 4 representatives and elected 4 representatives, it could be argued that they had received their fair share of the total representation.
The US Supreme Court has generally frowned on floterial districts, because in a case like that above, the voters of the larger county would comprise 5/8 of the electorate of the floterial district. In effect, the voters in the larger county would have an effect on the election of 2.625 representatives despite having a population equivalent that would entitle them to 2.5 representatives.
The Texas Constitution does not have any provisions for sub-county districts. That is, it provides that representatives be elected at large from the county. The US Supreme Court has also generally frowned on multi-member districts if they have a discriminatory effect. For example, a majority of the voters of Harris County could choose 1/6 of the members of the House, even though they might only barely represent 1/12 of the State's population.
In response to the Supreme Court one-man one vote decisions, the legislature passed a redistricting law that ignore all aspects of the Texas Constitution other than creating 150 equal population districts. This was challenged in the Texas Courts, and the Texas Supreme Court ruled that the Texas Constitution must be observed so far as the provisions of the two Constitutions could be harmonized. So, in Texas, representatives are still apportioned on the basis of whole counties, but then the larger counties are subdivided into single member districts. In place of floterial districts, a multi-county districts are drawn combining a part of a county, with all or parts of adjacent counties. No county with a population less than that needed for a single representative may be divided; and no large county may have some of its territoty be placed in more than one multi-county district.
After all the districts are created they are then checked for compliance with one man-one vote provisions of the 14th Amendment. In general so long as the districts are within 5% of the ideal population (95% to 105%) they will be upheld by the courts.
In Texas, it is usually impossible to fully comply with the Texas Constitution and meet the one man, one vote provisions of the US Constitution. But it is usually very close. In my map, there is one violation of the Texas Constitution, in that I would require the splitting of Ellis County, south of Dallas. The population of Ellis County is equivalent to 0.900 representatives, and there are no adjacent counties that it could join with to have enough population for a full district. So I have joined Ellis County with Dallas County to the north and Hill County to southwest, which together have a population equivalent to 15.972 representatives. There woud be 14 districts fully within Dallas County, with a 15th
overlapping slightly into Ellis County. The 15th district would include the bulk of Ellis County and all of Hill County.
The numbers indicate counties entitled to more than one representative, with the "+" sign representing a fraction of the county that will be joined with adjoining counties to form an additional district. Two counties, Bexar and Nueces have a population very close to that needed for a whole number or representatives, and all their respective districts would be contained within the two counties. Counties marked with a small "o" are counties with a population equivalent to between 0.5 and 1.0 representatives. This has no legal significance, but the counties would potentially cast over 1/2 the votes in the district.
