Couldn't tell you about Smith's personal arrival time at Marksville, but the lead elements of the Yankee column came into town sometime late in the afternoon on the 15th. There was a small skirmish as they came out of the Choctaw bottoms onto the Avoyelles Prairie, just north of Marksville. Union troops continued coming into town throughout the night.
Calliham's Plantation (frequently misspelled Callahan's) is in Hamburg, Louisiana, on Hwy 1, between Moreauville and Simmesport. The main house is still there - with solar panels on the roof, if you can believe that.