B. The coastal plains were near where the most immigrants come from.
The population distribution in the coastal plains region in early Texas was largely influenced by its proximity to the Gulf of Mexico. The coastal plains region was the first area that European settlers arrived in Texas, and many of these settlers arrived in the region via the Gulf of Mexico. The region's location also made it a natural gateway for immigrants arriving from Europe and other parts of the world, which further contributed to its population growth. Therefore, option B is the most accurate explanation for the population distribution in the coastal plains region in early Texas. The other options are not directly related to the population distribution in the region.