Rhoticity/non-rhoticity  ( americans.png showing general areas of non-rhotic pronunciation)
Copula/auxiliary deletion
Unmarked tense
Consuetudinal 'be'
African American Vernacular English 
American Midland
Appalachian
General American
Southern
Spanish
Dutch
German
French
Native American languages
folk etymology

Milestone Publications in American English

1786 Noah Webster, American Spelling Book (blue-backed speller)
1828 Noah Webster,  American Dictionary of the English Language
1919 H. L. Mencken, The American Language (several subsequent revisions)
1931 Leonard Bloomfield, Language
1949 Lorenzo Dow Turner,  Africanisms in the Gullah Dialect
1957 Noam Chomsky,  Syntactic Structures
1961 Merriam-Webster,  Third New International Dictionary
1985–2012 Dictionary of American Regional English (DARE); final volume published in 2012