National Journal posts, "Why Are So Many People Getting Sentenced to Death in Houston?" It's by Dustin Volz. You can see the entire list at the link.
Just 10 U.S. counties—roughly 0.3 percent of the nation's total—account for more than a quarter of all the American executions that have been carried out since 1976.
Texas's Harris County, which includes Houston, is far and away the leader in executions during that period. That district has handed out 122 death sentences that were carried to completion, more than double the next highest. Harris County alone is responsible for more executions than any state besides Texas.
Dallas County, which includes the Dallas-Fort Worth area, comes in second at 53.
Related posts are in the geographic disparity, prosecution and sentencing category index. You can also jump to coverage of a 2013 DPIC report on county prosecutions of capital punishment and to two sets of maps showing death penalty prosecutions by location.