The fourth of July is the day of freedom for the people of America. In the speech, Douglas comments on the celebration of the day and says that to celebrate such a day is very ironical. He says that the celebration of freedom which the people are celebrating is in reality still under slavery. Hopefully this helps :)
Puritan migration to New England (1620–40) ... The Puritan migration to New England was marked in its effects in the two decades from 1620 to 1640, after which it declined sharply for a time.
