We do not get a lot of facts, a lot of investigation, but there are many reports and they are spread over considerable time and distance. In 1860, Texans had major security threats from Commanches, Kiowas, and Mexican bandits. Relations with the Mexican government were not good. Generally, except for cities like Austin and Dallas, every place beyond East Texas (the majority of slaves were in East Texas) was a frontier and very vulnerable. From the news reports, all or most of the arsons and slave revolt plans were in Central, South and North Texas. I recall a few of them in the Houston-Galveston area, but that was the biggest port and there was also a lot of commerce in Beaumont and other parts of SE Texas where I have not read of any such trouble. It seems the slave and suspected arson problems were coincidently on the frontier where they would cause the most distress.