Most information on William McCormick family from family group sheets sent to the Kentucky State Library at P.O. Box 537, Frankfort, KY 40602, by Lois L. Hupfer, 3087 South Harlan, Denver, CO 80227. She is a descendent of Samuel Newton McCormick.

1820 census of Montgomery Co., KY, p. 239, line 29, lists:
Will McCormick, 3 m < 10, 1 m 10-15, 1 m 16-18, 5 m 16-25 (i.e., 4 m 19-25), 1 m > 45, 1 f < 10, 1 f 16-25, 1 f 26-45.

1830 census of Montgomery Co., KY, p. 35, line 11, lists:
William McCormick, 1 m < 5, 2 m 5-9, 4 m 15-19, 3 m 20-29, 1 m 50-59, 1 f < 5, 1 f 5-9, 1 f 10-14, 1 f 30-39, 1 f 80-89.

1840 census of Morgan Co., KY, p. 312, line 7, lists:
Wm McCormick, 1 m < 5, 1 m 10-14, 1 m 15-19, 1 m 60-69, 1 f < 5, 1 f 15-19, 1 f 50-59.

(These census readings are the basis of my listing William's birthdate as 1771-1775. The 1820 reading implies a birthdate of 1775 or earlier; the 1830 and 1840 readings imply a birthdate in the range 1771-1780, the overlap is 1771-1775.)

He does not appear in the 1850 census of Morgan or surrounding counties. I do not know whether he died or moved, though.

Possibly a sister of Alexander McClelland whose two daughters Ruth and Jane married two sons (John and Samuel) of William McCormick and Sally McClelland. If so, they would be first cousin marriages.