What is the proper way to address the US surgeon general in a letter?

The Proper address is Dr.& Mrs. Alfred Whatsit. If the Mrs has a doctoral degree as well, you may address them as The Drs. Whatsit , or Drs. Alfred and Eileen Whatsit ,no The if both first names are used,unless Mrs Whatsit is no longer practicing in her field of endeavor, then it's back to Dr. and Mrs. If Mrs. Whatsit is the DR, then you may put Mr.& Dr. , but most of the women I know with doctoral dgrees are happy to be Mr.& Mrs. to spare their husbands' ego,

Especially if their degree is something less valuable to society, like Liberal Arts.