Goldstone, Cynthia, and Avram Davidson. "Pebble in Time"
Divergence: 1846 CE
What if: The Mormons bypassed Salt Lake and settled near the San Francisco Bay.
Summary: A time traveler accidentally diverts Brigham Young and company.
Published: In The Magazine of Fantasy and Science Fiction, August 1970; Laughing Space: Funny Science Fiction (eds. Isaac Asimov and J.O. Jeppson), Houghton Mifflin 1982 (0395305195); and The Other Nineteenth Century: A Story Collection (eds. Grania Davis and Henry Wessells), Tor 2001 (0312848749BUY).