Which part of the history had to do with open borders creating Texas? Was it the Spanish explorers in the 1500s? The French? Was it Mexico's independence war? Texas independence war? Texas joining the Union? They don't call it the Six Flags over Texas for nothing http://www.lsjunction.com/facts/6flags.htm
"The Texas Revolution, also known as the Texas War of Independence, was the military conflict between the government of Mexico and Texas colonists, most of whom were land owners from the United States." - Wikipedia
They let a bunch of Americans settle in Texas because they basically had open borders and then they seceded in a huge land grab.
I think it had something to do with open borders...