Get boundaries to come through on states

Question

Edit 7 :

After quite a bit of help, I\'ve been able to get a map that is getting close to the results I need. But I still need to have the state boundaries come throug

Answer 1

The order in which you draw the layers matters. If you want the while lines on top, you'll need to add them last. And if you want the black shapes in the background, you need them first. So basically you need to split up the states into two draws: the background and the outline.

ggplot() + 
  geom_polygon(data=subset(map_data("state"), region %in% regions), aes(x=long, y=lat, group=group)) +
  geom_point(data = PRISM_1895_db, aes(x = longitude, y = latitude, color = APPT), alpha = .5, size = 3.5) +
  geom_polygon(data=subset(map_data("state"), region %in% regions), aes(x=long, y=lat, group=group), color="white", fill=NA)

which produces