St. Clair conundrum!

["J. Feagin" <feagin@home.com>]

My ancestor is Daniel H. St. CLAIR, b. abt. 1833 in IL, d. Aft. 1900 in
Tulare County, CA.  He m. Elizabeth ______ abt. 1870.  Their children:
Charles, Annie Pearl (my g. grandmother), Nellie, Frank, Maybelle, Mary,
Winifred, Leslie St. CLAIR.

Problem:  The Tulare, CA census shows Daniel ST.CLAIR b. 1833 in IL with
parents both b. in Germany!  How can this be?  Isn't ST. CLAIR a Scottish
surname?  There is a tradition in our family that someone in the St. CLAIR
family was adopted.  Anyone who can shed light on my ancestor and his
ancestors will be profusely thanked!

Regards,

John D. Feagin
Maryland