It may surprise you to know that I live in Polk Co., MO.I did not find your Reuben Alexander in the 1870 census of Polk Co. after I read the posting to which I am responding.
I do see that I have the wrong Alexander family, but perhaps they are kin to my line of McAlexanders. I note that there were some Alexanders who settled around Eudora, MO and at least two groups south of Pleasant Hope, MO.It is my belief that these all came to Polk Co., MO from Tennessee, except for one family which I will mention below. Which raises the possibility that they are desecendants of two more brothers of Samuel McAlexander, Sr. mentioned in my response to your original posting.James McAlexander (abt 1783-1861) and John McAlexander (abt 1792-1850/51) were both born in Virginia and they married sisters.
James married Ann W. Kidd in 1807 in Amhurst Co., VA; and John married Ruth Kidd in 1818 in Patrick Co., VA.These two brothers and their families migrated to the Lavinia Community of Carroll Co., TN where the two men lived with their families and died.
Amazing as it may seem, there was still a fourth brother who did live for a short time in Polk Co., MO.I have studied this family in great detail. This brother was Alexander James McAlexander (1796-1864) who was born in Nelson Co., VA and died in Platte Co., MO.(It had been reported to me earlier that he had died in Polk Co., MO which had aroused my curiosity, since I live in Polk Co.Actually, he is buried in a small family cemetery which today is located on the KCI airport property between North Kansas City and the air strip.) He and his wife, Sabrina Harbour (1802-1883), came to Polk Co., MO in 1838 and settled south of Pleasant Hope, MO.They came with sons: Claiborn, Edmund, James, David, and Charles.While living in Polk Co., they had three more children: William Benton, Matilda Sabrina Caroline, and Eliza Amanda Ann.(In the 1850 census, Claiborn and his wife were listed under Alexander, instead of McAlexander.)In 1852, the Alexander McAlexander family of Polk Co., MO moved to Platte Co., MO where yet another brother, William McAlexander, lived and where many of the descendants of these brothers would eventually congregate.
No, I did not find your Reuben Alexander in any census of Polk Co., MO.I have been privileged to examine sixteen entries from a family Bible of the Alexanders who settled around Eudora, MO and Reuben Alexander is not listed there, either.Sorry.