I figured our exports were higher after WWII and were dropping since, but it is basically the opposite.
There are two ways to look at that chart, and I think the correct one is that we used to produce a lot more of our own consumption.
Where our production used to be geared mainly toward servicing the largest consumer market in the world (us), it is now geared toward catering to niche world markets, such as jumbo jets and construction equipment.