Michael A. Gomez addressed the issue of Muslims in America in an article in the Journal of Southern History, LX (November, 1994) 4, 671- 710. Gomez analyzes the regions of the African coast from where Muslims could have been exported and concludes that Muslim slaves could have accounted for "thousands, if not tens of thousands," but does not offer a more precise estimate. It is likely that historians have underestimated the numbers of Muslims actually brought to North America. There is evidence of Muslims in North America in colonial records, but their numbers are limited and they probably came from the Senegambia.
     A number of Muslims are known to have lived in New Netherlands and New York in the seventeenth century, among them Anthony Jansen van Salee, whose Koran still exists. It is unclear what percentage of them arrived as slaves, but they appeared to have congregated in the vicinity of Gravesend in present day Brooklyn, which was known to have liberal religious attitudes.
     Despite the known existence of Muslims in early New York there are no known studies of them or their community. It is possible that the Muslim religion had some influence in laws prohibiting Africans from gathering together in Kings County, Long Island, after 1684. It appears that most Muslims eventually converted to Reformed Christianity in the New York City, region, though the community may have merely gone underground.
     Anthony and Abraham van Salee were among the earliest arrivals to 17th century New Amsterdam. In a number of documents dating back to this period, they are both described as "mulatto". From what scholars have been able to piece together about their background, they appear to have been the sons of a Dutch seafarer by the name of Jan Jansen who had "turned Turk" and become an admiral in the Moroccan navy.  With the Port of Salee as the base from which it harried European shipping, references to the fleet he commanded are salted away in the old English sea shanties that are still sung about the Salee Rovers. The mother of his two sons was probably a concubine he had while trading in this part of the world before his conversion to Islam.
     As a result of the anti-social behavior of his white wife, Anthony van Salee was induced to leave the city precincts of lower Manhattan and move across the river, thus becoming the first settler of Brooklyn. Since Coney Island abutted his property, it was, until sometime in the last century, also referred to as "Turk's Island"; the word, "Turk", being a designation of his which the records used interchangeably with, "mulatto". According to the documentation that people like Professor Leo Hershkowitz of Queens University have sifted through, it would seem that Anthony van Salee never converted to Christianity. His Koran, in fact, was in a descendant's possession until about fifty years ago when, ignorant of its relevance to his family's history, he offered it for sale at auction.
     The Van Salee history also includes a more contemporary black collateral branch in the U.S. Anthony's brother Abraham fathered an illegitimate son with an unknown black woman. The son became the progenitor of this side of the family. Although having to face constraints that their "white" cousins could at best only imagine, two of these van Salees nevertheless left their mark in the annals of African American history.
     Dr. John van Salee De Grasse, born in 1825, was the first of his race to be formally educated as a doctor. A member of the Medical Society of Massachusetts, he also served as surgeon to the celebrated 54th Regiment during the Civil War. His sister, Serena, married George Downing who was not only an enormously successful black restaurateur both in New York City and in Newport, RI, but a man who used his wealth and connections with the East Coast's most powerful white families to effect social change for his people. Because of his organization and his own contribution to the purchase of Truro Park in Newport, one of the streets bordering it still bears his name. Interestingly enough, this genealogy was done as part of an ongoing study of the Ramopo in Tappan, NY, one of those red, white and black groups sociologists and ethnographers are now working on and which in academies are referred to as "tri racial isolates". It is because of what advantages their Indian heritage (no matter how discernibly negroid they were) legally and officially provided them that the opportunity for "passing" in these groups was not only a more ambiguous political or moral decision but, comparatively, a more easily documentable one as well.

Genealogical note:  Family lines of American historical importance that can trace lines of descent from this ancestry
John Hammond of Columbia Records
Vanderbilts
Jackie Kennedy Onassis
Whitneys
Humphry Bogart

A more complete article on Anthony and Abraham van Salee can be viewed on the internet as part of a PBS Documentary - The Blurred Racial Lines of Famous Families

Additional sources of information:
Hoff, Henry B. "Frans Abramse Van Salee and His Descendants: A Colonial Black Family in New York and New Jersey," The New York Genealogical and
Biographical Record. Vol. 121, No.2 (April-October 1990): 65-71, 157-161,   205-211.
 
New York Genealogical & Biographical Record, vol. 103, p. 16. The Washington-McClain Ancestry, by Charles A. Hoppin, vol. 3