William Cicero Grant was born in 1815 and died in Detroit, Michigan in 1883.  Charles Crosman was born in 1830 and died in 1907.   The firm of Grant & Crosman operated from 1858 to 1861 in Detroit, Michigan.

Reference:   Smart, Charles E.  The Makers of Surveying Instruments In American Since 1700   Troy, New York:  Regal Art Press.  1962

Burt & Watson (1857-1858) - In 1857 John and William Burt, almost certainly with their father's help, were able to entice Thomas N. Watson, William Young's foreman at the the time and an excellent instrument maker, to move to Detroit and become a partner in the firm of Burt & Watson.  The earliest evidence of this move is an invoice dated June 20, 1857:  "Rec'd from W. A. Burt two Hundred dollars for one solar compass to be finished in one year. T. Watson."  This was probably money advanced by William A. Burt to Thomas Watson to help with moving expenses.  The firm is only listed in the 1857 directory.  On the death of William A. Burt the family lost interest in the business and on October 23, 1858 the Detroit Advertiser announced:  "GRANT AND CROSMAN have purchased the establishment of Burt & Watson, next door to the Advertiser's office, for manufacturing Burt's Solar Compass and Mathematical Instruments generally."  Thomas Watson is listed in the 1859 Detroit directory and does not reappear in the Philadelphia directories until 1861 suggesting that he left Detroit in 1860.

Grant & Crosman (1858-1861) - Both Charles Crosman and William Grant had been employed by Burt & Bailey and Burt & Watson as instrument makers.  The firm of Grant & Crosman is only listed in the 1861 Detroit directory.  However they seem to have been in business from 1858 through 1861 at the old location on Jefferson Avenue.  In 1862 Grant moved the business to 11 Woodbridge and changed the name to William C. Grant.  Charles Crosman appears to have left the firm at this time.  Grant continued at various addresses until 1873.