RJ, you obviously got it right. The last photograph is of Captain W. J. McDonald, Company B of the Texas Rangers. The following is taken from the web site of the Texas Ranger Hall of Fame (
http://www.texasranger.org/history/SilverStars1.htm):
ONE RIOT, ONE RANGER
The law authorized for Ranger companies a maximum of 20 men each. The career of Co. B. Capt. W. J. McDonald, and a book written about him, added much to the Ranger legend, including two of its most famous sayings.
The often cited "One Riot, One Ranger" appears to be based on several statements attributed to Capt. McDonald by Albert Bigelow Paine in his classic book,
Captain Bill McDonald: Texas Ranger. When sent to Dallas to prevent a scheduled prizefight, McDonald supposedly was greeted at the train station by the city's anxious mayor, who asked: "Where are the others?" To that McDonald is said to have replied, "Hell! ain't I enough? There's only one prize-fight!"
And on the title page of Paine's 1909 book on McDonald are 19 words labeled as Capt. McDonald's creed: "No man in the wrong can stand up against a fellow that's in the right and keeps on a-comin'." Those words have evolved into the Ranger creed.
Thanks, guys, for playing along. As a kid back in Oklahoma, I grew up on this stuff.