The birthdate for Jacob could be 1825.

Enumerated as Jacob (a. 22, bp. VA, "Gold Hunter") living with his father Jacob McReynolds in the 1850 Census for LaFayette County in Missouri.

Listed in the 1852 California Census for Sonoma County (recorded on 20 Aug 1852), page 40, as Jacob McReynolds (a. 25, bp. VA, last residence: MO, occupation: Farmer). Listed with his brother, Will McReynolds (a. 28, bp. VA, last residence: MO, occupation: Farmer) and his wife, Virginia McReynolds (a. 17, bp. AR, last residence: AR).

Marriage data is from the Cooper Family Bible (see additional material under Talitha). Both Jacob and Talitha appear to have been members of the 1853 Cockrill-Hagans Wagon Train.

From McReynolds Family Westward Bound by Glenva Conklin (copied for me by Susan Zeni) pp. 38:

Jacob was born in Washington County, Virginia and moved to Illinois then to Missouri. In 1849 he crossed the plains in California with his brother William and cousin George Ragle. He made several trips back to Missouri, helped his folks to make the Westward journey in 1852 and again in 1853 he made the trip to marry Tehitha. They settled in Green Valley in Sonoma County, California near their parents. It was here that all their children were born. Tehitha died of consumption after her last child was born and is buried in Spring Hill Cemetery near Sebastopol, California. In 1882 Jacob with his children moved to Battleground, Washington State. He died there and is buried in Lone Fir Cemetery, Portland, Oregon. He has many descendents in Oregon and Washington.

An obituary For Jacob McReynolds in an uncited Santa Rosa Press Democrat (from McReynolds Family Westward Bound by Glenva Conklin, pp. 38-39):

OVER THE DIVIDE

Jacob McReynolds Formerly of Sonoma County Dies at His Home in Washington

Last Saturday morning the Press Democrat annouced that Jacob McReynolds, one of the well known pioneer family of that name in this county, was seriously ill in his home at Battleground, near Vancouver, Washington, and not expected to recover. It is learned that he died there early Sunday morning and was buried Monday afternoon in the family plot on the side of his mother at Lone Fir Cemetery, Portland, Oregon. The deceased was a native of Virginia and would have been 84 years of age October 19 of this year. Jacob McReynolds came to this State from Missouri with his brother James and first lived in the old El Dorado building at Sonoma, which is now being torn down to make way for a modern structure. He aftwards located with his brother on a large tract of land in Analy township. The McReynolds brothers were James, Jacob, William, Stephen, and Isaac and are all dead except William and possibly Isaac, who disappeared many years ago and whose whereabouts are unknown. The children of the late Jacob McReynolds are William, Lewis, Charles N., Edward, Fredrick, Mrs. Emma Upson of Reno, Mrs. Mattle Boyington and Mrs. Hettle Gist of Gist, Oregon, the latter a sister-in-law of John Gist of this city.
Jacob McReynolds all his life was a good man and under the fir trees in the northern cemetery he sleeps in peace and honor, and no better reward hath the dead.