I found this photo from Summer 2016. It is the USA map I have just finished with a red pin for each National Park Service unit. At that point there were 418, now 424. I had not yet put in the yellow pins for the 40 or so parks we had visited. So as we visited and photographed a park, the red pin was replaced with a yellow pin. We are currently at 357 parks with 67 to go, a few of those are very unlikely but we are still looking at over 400.