Harlem Missouri is now part of North Kansas City. It was North of the Missouri River in the bend in Clay County across from downtown KC. This would be in the vicinity of the downtown municipal airport. It was a separate community in 1861 about 3 miles from Randolph. This 1888 Map shows it well:
http://localhistory.kclibrary.org/cdm4/item_viewer.php?CISOROOT=%2FMaps&CISOPTR=1545&DMSCALE=12.5&DMWIDTH=750&DMHEIGHT=532.984061393&DMMODE=viewer&DMFULL=0&DMX=260&DMY=184.507969303&DMTEXT=&DMTHUMB=0&REC=18&DMROTATE=0&x=369&y=271

There are several photos in this collection of Harlem in 1881 during a flood.

John R