st. clair county is a county in the u.s. state of alabama. as of the 2010 census, the population was 83,593. it has two county seats in ashville and another in pell city. it is one of two counties in alabama, and one of 33 in the united states, with more than one county seat. the name is in honor of general arthur st. clair, an officer in the french and indian war.