Yes, that's the entire length of Park Street, from number 6 all the way down to number 0. (Is Massachusetts the only place where street numbering frequently starts with zero instead of one or two?) Houghton Mifflin was located in two buildings on Park Street, number 4 and number 2; neither survives.
Copyright 2004, Garrett Wollman. All rights reserved. Photograph taken 2004-05-01.