Wikipedia is wrong (but nice to note its been updated to include WA). As far as I'm aware of from the ABA checklist, there are three previous records for the ABA area (they didnt include TN): (By the way, I was lazy and copied the below details of each sighting from a post Ian Paulsen had posted on another list).
1) Biddleford Pool, York Co, ME 5-11 Nov. 1977.
2) Reelfoot Lake, Obion Co., TN 13-15 May 1984.
3) Toronto Islands, Toronto, ON Canada 7 Oct. to 6 Nov. 1993.

Source: ABA Checklist 6th edition 2002.

Assuming nobody suddendly discovers a band on the birds leg... should be:

4) Windust Park, Franklin Co., WA 6-7 Sept. 2008 (Unless it is seen again).

Most guides that mention its vagrancy including Nat Geo mention ME, TN and ON records. The bird seems to show a pattern of long range overshooting and notice that while 3 records occur from Canada or states bordering Canada, no records from CA, NM, TX, or AZ.

Scott Downes
downess at charter.net
Yakima WA