Complex sentence: On the national level, Dalton is represented in the United States House of Representatives as part of Massachusetts's 1st congressional district and was represented by John Olver of Amherst from 1991 to 2013, until Olver retired and Massachusetts was redistricted.
Split into simpler sentences: On the national level, Dalton is represented in the United States House of Representatives as part of Massachusetts's 1st congressional district. MA-01 was represented by John Olver of Amherst from 1991 to 2013, until Olver retired and Massachusetts was redistricted.