Some of the colonists from England settled there and most of them carried a gene for deafness. Hearing people also knew and used the language.
Laurent Clerc
Gallaudet was a preacher but later wanted to study/learn methods of teaching for deaf people, so he traveled to England but got rejected by the people that were in charge because they didn't want to give away their secrets.
First deaf school is established in the US
We have made so much progress. This will make a change for history.
Gallaudet then traveled to paris were he was welcomed to the school for the deaf which there they used sign as a teaching method. There was where gallaudet met Laurant Clerc.
Deaf School influencing ASL
No,we don't want you here.
Gallaudet managed to convince Clerc to go back to America to establish a school there for the deaf.
The first school for the deaf in America is established (1817).
The school started with a mix of signing gesture systems from different people but they were exposed to each other and ASL was made out of the mix.