This is not a direct answer to your question, but may lead you to some primary sources. The Mother Mosque of America in Cedar Rapids, Iowa was erected in the 1930s. It is considered to be the first permanent building specifically used as a mosque in the entire United States. Though built well after initial settlement of the area, it is probable that a Muslim community was there beforehand (to warrant its construction). Their records might indicate how early the first Muslims arrived in Eastern Iowa or elsewhere across the country.

Their information can be accessed here.

Wikipedia indicates that Ross, North Dakota had a mosque that predated the Mother Mosque by several years but was later torn down. Investigating that community may be helpful as well.

edit: punctuation