Complex sentence: Averill then moved to Winthrop, Maine, and engaged in mercantile pursuits for three years; moved to northern Pennsylvania in 1852 and again engaged in lumbering until 1857, when he settled in Lake City, Minnesota.
Split into simpler sentences: Averill then moved to Winthrop, Maine, and engaged in mercantile pursuits for three years. In 1852 he moved to northern Pennsylvania and again engaged in lumbering-until 1857, when he settled in Lake City, Minnesota.