MD is the only state in the Union, as to the best of my knowledge, wherein USCIS does allow ASCs (fingerprint location) to conduct US Civics and English test at the time of fingerprinting. It's not a mandatory, though. It's up to the applicants as to whether or not they like to take their test on US History and Civics at the fingerprinting location at the time of fingerprinting.
Since you live in MD, you may contact the fingerprinting location there to find out if they do take the test at thier place or not. And if they do then you may decide if you like to take your test over their or at the interview. Choice is yours.