From 1879 to 1881, Simpson was a member of the Newburyport school committee. He then served on the city's board of aldermen.[6] In 1883, he represented the 16th Essex District in the Massachusetts House of Representatives.[7] In 1885 he served as the mayor of Newburyport.
In 1882, Simpson and a group of Massachusetts businessmen formed the Altamonte Land, Hotel and Navigation Company. The company began purchasing land in the area of Lakes Orienta, Adelaide, and Florida and in 1883 opened the Altamonte Hotel. The area became known as Altamonte Springs, Florida. One of the streets in the new community was named Newburyport Street after the hometown of Simpson and many other of the company's investors.[10]
In 1884, Simpson and David L. Withington purchased the Plumb Island Bridge and a small hotel on the island. They sold the property three years later.[11]
In 1886, Simpson and seven others founded the Newburyport Street Sprinkling Association, which watered properties on a few streets in the city. The association was dissolved the following year after the city of Newburyport took over responsibility for watering the streets.[12]