I have lived in Dallas for quite some time, and had the opportunity to run the Dallas White Rock Marathon now known as the Dallas Marathon. The Dallas Marathon usually takes place in early December and is sufficiently spaced out from the other Texas marathons to prevent any conflicts or a situation where one marathon would draw runners from another. Generally the other "big city" marathons in Texas are Houston, San Antonio, and Austin. (No offense to the Cowtown Marathon in Fort Worth which I will be doing later in the month.)
This past week, the San Antonio Rock 'n' Roll Marathon announced that it was going to take place on December 8, the same date as the Dallas Marathon. A few folks in Dallas got upset over this and it turned out that there was actually a contract provision between the 2 marathons that prevented such a conflict. The provision provides that the San Antonio marathon:
shall refrain from sponsoring, producing, organizing, promoting, managing or conducting any marathons, half marathons, relays or other running events or events with a running component in the State of Texas from December 1 through May 31 each year for the life of our agreement…
Even though Dallas and San Antonio are 275 miles apart, marathon organizers were concerned runners would go to San Antonio instead of Dallas. One report estimated Dallas would lose 700 runners.
Things were ironed out and later last week it was announced the San Antonio marathon has moved its date from December 8 to November 17, 2013.