The only likely fit I find is a Mark Fortchau/Fortune listed in the 1870 census St. Clair Co Illinois (just across the river from St. Louis) Born 1840 in England he is listed as a grocer. Married to Anna (25, Scotland) with son George (4, Missouri) and daughter Mary E (2, Illinois)?

As a Grocer he would need access to the docks, as an emigrant he may not be in an 1860 census and his son was born 1866 in Missouri.

FWIW