John Udell was an American farmer and Baptist lay preacher who is primarily known for two detailed diaries he kept of his travels to California across the Great Plains of the United States. He traversed the overland route four times between 1850 and 1859, returning by sea on his first three trips. After his fourth and final trip to California he remained there, settling in Solano County and later in Sonoma County. His first diary, Incidents of Travel to California Across the Great Plains, was published in 1856. His second diary, Journal of John Udell, Kept During a Trip Across the Plains, was first published in 1859 and is an account of his last trip to California as a member of the Rose-Baley Party.

The Rose–Baley Party was the first European American emigrant wagon train to traverse the 35th parallel route known as Beale's Wagon Road, established by Edward Fitzgerald Beale, from Zuni Pueblo, New Mexico to the Colorado River near present-day Needles, California.