Pierse was the son of an Irish immigrant who had originally traded with merchants from Ireland who were based in Portsmouth.
After completing his elementary schooling, the young Long became an apprentice to another businessman named Robert Trail.
He dealt primarily in the trade of timber to the West Indies as well as the importation of goods from England and Ireland.
As the start of the Revolution drew closer, he joined Portsmouth's Committee of Safety to help keep the city safe.
On April 13, 1789, Long died in his home in Portsmouth, and he was laid to rest in the Proprietor's Burying Ground in that city.