A special election is scheduled March 3 to fill the remainder of his four-year term. Argall was selected in a meeting Saturday in Pottsville.
Argall was among the six people who expressed interest. The others were Ed Balkiewicz, Willard Dellicker, Joseph Gattone Jr., Chris Hobbs and Gretchen Sterns.
The district covers all of Schuylkill County and parts of Berks, Carbon, Lehigh, Monroe and Northampton counties.
The state Democratic Party is expected to vote on its nominee in about a week.