ship carvings

[Dave Stevens (Lumberyard)]

back when the US built the first frigates Hancock, Raleigh, Confederacy and the Oliver Cromwell i noticed at the stern a figure in the center and figures on the right and left of center male and female except the Oliver has 2 females

There seems to have been a theme as to who these figures represent and who is the center bust of? is it lady liberty? is it Martha Washington? Why is the figure on the the first one wearing a crown?