What time period was the TV series Gunsmoke set in?

This is an interesting question. The original 1/2 hour shows started with Matt making a speech while he was walking out on Boot Hill (the burial site located out from town). The markers clearly show dates of 1872 and 1873. Now, Dodge City wasn't really Dodge City until 1872, and then they didn't get a Marshall there until 1875. If we suppose that the writers are trying to stay true to life, then I would say from 1875 on. Guns, gunbelts, rifles, saddlery, etc., are not true to period, but so what?! Just sit back and enjoy the story.