This table shows the decennial Census count of the state and current counties from 1900-2010. The following table includes the decennial count for the state and counties, including historic county names in use at the time of the Census. Finally, these are the notes from the 1920 Decennial Census that explain the name and boundary changes to counties between 1860 and 1920.
The US Census Bureau's QuickFacts page provides the most recent information on the State, Counties and about 50 cities. You can access QuickFacts online, then use the drop down menu to find the county you are interested in.