Component Models: LSM
The primary thing to note is that an _FillValue must be assigned, and the coordinate arrays must be renamed.
mpFillColors = (/0,9,28,25/) selects which colors out of the default color map to use in the plot. First is the foreground, black, which is used for the lines, next is the background which is normally white, but in this case is light blue. Then there is a light gray for the continents, and finally, a green for the lakes. If you left off this last value, the lakes would be colored blue like all the other missing values. Note we do not turn on color fill here.
mpOutlineBoundarySets = "AllBoundaries", Will draw both US State boundaries and other national boundaries.