Sorry for my delay in responding.There was definitely an Allen D. Ratcliff who was living in Catahoula Parish in the 1840s.In addition, according to Ancestry's Mississippi Marriages, 1776-1935, an Allen D. Ratcliff married a Blendia B. Davis in Amite County, MS, on October 30, 1826.
Here is the information on Isaiah, published in Biographical & Historical Memoirs of Northwest Louisiana, published by the Southern Publishing Company in 1890 - hope it might help you or some other researcher:
Isaiah Ratcliff is a Georgian by birth, and like the majority of native-born residents of that country he is thrifty, industrious and public spirited.He was born in Gwinnett County, September 21, 1827 to Joseph and Annis (Johnson) Ratcliff, both of whom were South Carolinians, in which State they were reared and educated, the father being a farmer by occupation.He moved to Georgia at an early day, settled in Gwinnett County and afterward in Muscogee County, where he resided until 1836, at which time he came to Russell County, Ala., where he resided for eight years.He moved to Walton County, Fla., for five years; then to Bienville Parish, La., in 1851, and here passed from life on October 27, 1857.While a resident of South Carolina he served as captain of a company of militia, and after coming to Bienville Parishhe held the office of justice of the peace.At the time of his death he was sixty-four years of age.Isaiah Ratcliff was reared in three states:Georgia, Alabama, and Florida, and when still young he came to Louisiana (in 1849) and settled in what is now Webster Parish within seven miles of Minden, the first two years being spent on a farm.He then turned his attention to carpentering and building, continuing up to the war, and also worked in a cotton-gin factory for some three and one-half years, having charge of the wood mechanical part of the work for some time.In 1862 he became a member of an independent company of cavalry (the Minden Rangers), and served until the close of the war in Capt. Webb's company, which acted as escort for Gens. Armstrong, Crosby, and W.H. Jackson.Mr. Ratcliff returned home May 28, 1865, and for some time thereafter was engaged in milling.In 1868 he purchased a farm, which he improved, and in 1872 made the purchase of a mill.Later he purchased his present farm of 440 acres to which he moved his mill, building also a cotton-gin thereon.He was appointed and served nearly ten years as a member of the school board and in July, 1888, was elected a member of the police jury and served four years.He was a member of, and takes an active part in, the Farmers' Union, and holds the office of chaplain of the parish union, and of his own local union.He joined the Baptist Church in 1847, and has been a member of it since that time, being now a deacon.He is a consistent Christian gentleman, and a man possessing many sterling traits of character.He was married in Minden January 12, 1853, to Miss Caroline W. Harrison, a daughter of W.C. Harrison, her birth occurring in Twiggs Couty, Ga., although she was reared in Louisiana.Mr. and Mrs. Ratcliff have ten children:Allen H., Perry D., Anna (wife of J.W. O'Neal), Elizabeth L. (wife of J.M. Rickerson), Mary F. (wife of Wimberly Baker of Bienville Parish), Leary, Hattie L., Joseph H., Carrie A. and Bessie Lee.Mr. Ratcliff, his wife, and all the children with the exception of two, are members of the Baptist Church.