Post-Office-3rd-and-Unionb-then-WEB March 8, 2015 1200 × 916 Seattle Now & Then: Going Postal at Marion & Western Central Post-Office at the southeast corner of Union Street and Third Avenue. This is the accepted Chuckanut stone, while the Colman Annex is made of the first stone ordered for the P.O., but then rejected by the Feds.