Hi Jude, There is a family tree at www.ancestry.com for Larkin Reynolds. You can access it even if you don't have a subscription to Ancestry.com.
In 1870 he was living in Washington Co., OR. Larkin Reynolds, b. MO, 39 yrs old, common laborer.
In 1900 he was living in Beaver Dam, Washington Co., OR. Larkin Reynolds, b. MO, Jan 1830, divorced, farmer.
There might have been an obituary for him. There are a couple of volunteer who will look up obituaries in Random Acts Genealogical Kindness. Go to www.raogk.org, read instructions, choose Oregon, choose Washington County and choose one volunteer. Successful Searching!