A gang could mean a gang of outlaws or a group of men who ran together such as gamblers. Some people looked upon gamblers as unsavory characters and might refer to them as a “gang of” this or that. The “Dodge City Gang” you mention weren’t really a gang and were euphemistically known as “Luke Short and his Dodge City Peace Commission.” Luke had been a central figure in the “Dodge City War” that began when reformer Larry Deger became mayor and passed ordinances against prostitution. Under the ordinances the shady ladies could be arrested as vagrants.
Luke was house dealer at the Long Branch and technically it became a brothel. When some of the ladies were arrested he took umbrage. At the same time Luke and some other gamblers were escorted out of town. Luke rounded up his pals Wyatt, Bat, and Charlie Bassett and they took the train to Dodge. Mayor Deger prevailed upon the governor to send in the militia but instead he sent a man in to mediate. The mayor backed off while Luke and his friends posed for the famous photograph, thus ending the “war.” Luke and his partner sold the Long Branch in 1883 and he wound up in Fort Worth where he died with his boots off in 1893.
The real Dodge City Gang described a bunch of hard cases including “Dirty” Dave Rudabaugh, “Mysterious” Dave Mather, and leader, Hyman Neil, better known as Hoodoo Brown, who headed for lawless Las Vegas, New Mexico when it was a raw, boisterous boom town. Lesser-known were Bill “Slap Jack” Nicholson and John “Bull Shit Jack” Pierce. During 1879-1880 they attempted to dominate the political and economic life there. Hoodoo and the gang murdered, stole, robbed trains and stages. Other than that they were upstanding citizens of the community.
Finally the citizens tired of their shenanigans and with the help of vigilantes started tossing them in jail. Las Vegas became famous for its use of a “hanging windmill” to administer a suspended sentence to the bad guys.
The gang’s demise after a few months was caused mostly by greed and open defiance of the law. Even though Hoodoo is not as well-known as many other outlaws, some claim he was worst of them all.