This website documents the Family History for two Dunn families who immigrated to the British Colonies (eventually to become the United States of America).
The earliest Dunn family was probably William Dunn, an early Scot colonist who arrived in about 1716 in Virginia.
The other Dunn family comes down from Simeon Adams Dunn, the son of Simeon Dunn and Hannah Gustin of New Brunswick, New Jersey. That line goes back to James Dunn, an early (1680) settler of Windham, Connecticut.
The two Dunn lines join when John Johnson Dunn married Sarah Sophia Dunn. through Sarah Sophia, the Dunn family links back to the Mayflower passenger, John Alden.