I've always loved collaborative timelines, and even with Viva Colombia on my hands, I've been itching to do one. So. Here it is, and here are the rules:
1. You cannot post any date past 1845 until all the dates before have been filled satisfactorily.
2. No assassinations or random killings of politicians unless you can get two other posters to support you.
3. More of a trend-setter: try and keep the first few PoDs small changes, and then let them butterfly into big changes later on.
I'll start:
February 19, 1839: Mirabeau Lamar's extermination campaign against the Comanches in West Texas ends successfully, with the Comanches being forced to move out of Texian territory.
August 23, 1841: Austrian gunsmith Reinhard von Neuttingen, inspired by the scientific works of Johann von Goethe in optics, builds a primitive optical rifle scope and tests it out in his home village of Schwaz: he is able to fire accurately for over 400 meters.