Star Trek: Enterprise - North Star Season 3 Episode 9
The crew of the Enterprise discovers about 6,000 humans on a Delphic Expanse planet living in settlements that are similar to those of the Old West. Archer, T'Pol and Trip disguise themselves and head down to observe, hoping to learn how these settlements came to be. Reporting from Enterprise, Reed notes that scans indicate that there's also a nearby settlement of aliens.