The quotes below by Daniel Merrill (Born in Rowley, Essex County, Massachusetts, 18 March, 1765: died in Sedgwick, Hancock County, Maine. 3 June, 1833) gives testimony that Baptists throughout America in the nineteenth century believed in Baptist perpetuity based upon Matthew 16:18.
"The origin of the Baptists can be found no where, unless it be conceded, that it was a Jordan or Enon. ... The Hussites, in the fifteenth century, the Wickliffites, in the fourteeth and the Petrobrussians, in the twelfth, and the Waldenses, were all Baptists. ... The consequences of this whole is this: The Baptists have no origin short of the apostles. They arose in the days of John the Baptist, and increased largely in the days of our blessed Saviour, when he showed himself unto Israel, and the days of his apostles, and have existed, under the severest persecutions, with intervals of prosperity, every since. ... In this short history of the Baptists, we see the continued accomplishment of one of Christ's promissory predictions, which is, Matt. 16:18, 'The gates of hell shall not prevail against the church.'" -- Daniel Merrill
(Daniel Merrill was a minister among the Congregationalists, but in 1805 he became convinced of the truth of scriptural baptism and became a Baptist. He was ordained to the Baptist ministry at Sedgwick, Maine on May 15, 1805. Shortly after his ordination he preached a series of seven sermons on the Mode and Subjects of Baptism which was published that year. He later added a eighth sermon to this series entitled "A Miniature History of the Baptists". The tenth edition was published in 1812.)