What is the A. in Sanford A. Hooper?

Try as I might, I get a dead end everywhere I look for the answer to this question. I don't know why it bugs me so much not knowing his middle name. Perhaps if he weren't so consistently identified as "Sanford A. Hooper" or "S.A. Hooper" in all the documentation I can find, it wouldn't matter. But the "A" was obviously important to him, and I really want to know what it stands for!