1860 census of Rowan Co., KY, (June 10) lists on p. 9, #64:
Samuel Clark, 20, VA, living alone. This entry is right after the entry for the George B. Clark family, which also has a male age 20, name something like "Sanel". Possibly Samuel was recorded twice because he was at his parents when the census taker came by?

1870 census of Rowan Co., KY, (taken June 8), Christy Creek precinct, lists on p. 3, family #15:
Clark, Samuel, 31, farmer; Elizabeth, 22; Amanda, 4; Melissa, 12; America, 8/12, b. Sep. All born in Ky except Samuel born in Va.

1880 census of Rowan Co., KY, Christy Creek precinct, lists family #417:
Clark, Samuel, 41, farmer; Elizabeth, 32; Amandy E., 14; Malissa, 12; America, 9; John C., 8; William, 5; Martha, 3; Franklin, 3/12, b. Feb. All born in Ky except Samuel and Elizabeth and their parents born in Va.

According to the birth records, Martha was born 3 Dec 1874, so should really be 5, not 3. This suggests that William must really be older as well, probably 6 1/2, but perhaps even as old as 7.

Notice that this census does not list Amos, who was listed as age 22 in 1900, nor Minnie M. Clark who married Martin Fraley. It may be that Minnie is not really Samuel’s daughter, but Amos was listed as Samuel’s son in the 1900 census.

1881 Tax Rolls of Rowan Co., KY, lists on p. 5, lines 7-13:
Samuel F. Clark, 100 & 15 acres neighbor John Black, 40, 10 & 10 acres neighbor Jas Abbot, 400 acres neighbor Wm Boyd, 200 acres neighbor Martha Cox, 1 male over 21, 5 children 6-20. (People in other categories not enumerated.)

1885 tax rolls of Rowan Co. lists on p. 7:
Samuel F. Clark, 100 acres neighbor Wm Kegley, 1 m over 21, 6 children 6-20 (other categories of people not enumerated), 34 acres neighbor Wm Tabor, 42 1/2 acres neighbor Wm Tabor, 27 acres neighbor Polly Trent, 3 acres neighbor Wm Kegley, 300 acres neighbor Wm Kegley.

1890 Tax Rolls of Hogtown Prec., Rowan Co., KY, lists on p. 29, lines 18-22:
Samuel F. Clark, 42 acres neighbor Warren Alderson, 27 acres neighbor Polly Trent, 63 acres neighbor J. Petit, 150 acres neighbor J. Black, 2 acres neighbor H. Kegley, 1 male over 21, 6 children 6-20. (People in other categories are not enumerated. I did not record other property as there were 100 columns for each line in this register! There was a pencilled in bracket next to these 5 lines with the note "Ex671" - perhaps a reference to an estate execution number?)

1900 census of Rowan Co., Ky, Hoggtown precinct, enumerated 17 June, lists on p. 8B as family # 139:
Samuel Clark, widower, age 61, b. Apr 1839, in Virginia; Malisee Petit, dau., 32, b. Feb 1868; <plus her four children - see John P. Petitt notes for that part>; Amos Clark, son, 22, b. May 1878; Noah, son, 19, b. Jan 1881.

I don't know why Amos isn't listed in the 1880 census.