Dawn, I'm not sure it was a "specialty crop" before 1940's. My mother-in-law, 
who was born in 1925 in Lexington County, SC, talks about her father growing 
it and the children helping pack it in crates for the market.
And, hey, asparagus grows well in middle SC (I visited a relative who lived 
in a gorgeous home--their back yard had the biggest, most beautiful crop of 
asparagus I have ever seen!). It certainly is a tasty vegetable. I say we 
need to eat more of it. I LOVE it!  Sandra