Whiteside was elected as a Republican to the Fourteenth and Fifteenth Congresses. He resumed the hotel business in Lancaster and served as register of wills and again a member of the Pennsylvania House of Representatives in 1825.
Whiteside was elected to the Fourteenth and Fifteenth Congresses as a Republican. He resumed his business interests in Lancaster, including serving as register of wills and later rejoining the Pennsylvania House of Representatives in 1825.