If you download Oregon Pub 17 and start reading on page 77, you will find that the accumulated Interest from Treasury bonds, etc are tax exempt for an IRA distribution on a pro-rated basis. There is a very good worksheet that demonstrates how this works. I would imagine that this would have to be the case for all states, but maybe not spelled out as well as Oregon does in Pub 17. Believe me, if Oregon didn't have to exempt it from income taxes, they wouldn't.
*** I can not vouch for any State other than Oregon ***
