Immigration And Population In America From the 1600’s to the 1860’s, America experienced a massive growth in population numbers. Immigration had played an important role in this progress. However, the American people and their government were not prepared for expansion. Their response was not surprising for a newly founded nation still searching for its’ own identity. William Penn, a British colonial official, encouraged people of Holland, France, and Germany to colonize in the 1680’s. Immigration in the 1700’s was again encouraged greatly by the British. Lax policies on citizenshi