Yes, many of them ended up in the US Post Office in Willingboro, NJ.
IIRC, the government tore the entire building down and built a new one. They decided that they couldn't guarantee a good decontamination of the old building.
http://usatoday30.usatoday.com/news/nation/2005-03-14-anthrax-cleanup_x.htm
The building was cleaned up, it is on the corner in Rt 130 and the home depot in Hamilton NJ, it is still there and still a post office