3-5 Park Street
Later and long-time home of Woman's Journal and many suffrage organizations. See map here. Below are some great old photos of the site. I used the first one in my book Summer Suffragists.
Great photo of Park Street, which runs up the hill from the Park Street Church at right to the State House. Boston Common is on the left. Park Street subway stations are in the foreground. In the middle of the Park Street block, the lighter colored buildings were 3-5 Park Street.
E. Chickering & Co., "One panoramic photo of Park St. Station, showing Park St. Church and State House in distance, Boston, Mass.," about 1903 (edited). Courtesy of Library of Congress, https://www.loc.gov/item/2007661060/.
Marr, Thomas E., -1910. "Park Street Church, looking north, April 1, 1906," 1906, Boston Pictorial Archive, Boston Public Library, Digital Commonwealth, https://ark.digitalcommonwealth.org/ark:/50959/nv935h56j
From the left, the second building is No. 9 Park Street, then another building intervenes before 3-5 Park Street.
"Boston. Streets. Park Street, from State House." 1858, Boston Pictorial Archive, Boston Public Library, Digital Commonwealth, https://ark.digitalcommonwealth.org/ark:/50959/nv935g20z
In this 1918 photo, looking up Tremont Street, Park Street is barely discernable in the far center, but lighter colored buildings stand out as likely 3-5 Park Street. The State House is at the left in the distance. In the foreground, center, are the Boylston Street entrance and exit buildings of the Tremont Street subway. Boston Common is at the left. The light colored column is the Boston Massacre Monument, also known as the Crispus Attucks Monument, dedicated 1888. See Geo. H. Walker & Co. "Map of Boston Common and Public Garden," 1901, Norman B. Leventhal Map & Education Center, Boston Public Library, https://collections.leventhalmap.org/search/commonwealth:1257b9784.
To the right, one of these buildings (since demolished) held the headquarters of the Boston Equal Suffrage Association for Good Government (BESAGG) from 1916 to 1918. It was at 167 Tremont. My guess is it was just to the left (in this photo) of the nearly black six-story building. For more information, see this page.
The Parkman Bandstand, built in 1912, would be left of the Boston Massacre Monument, outside the frame of this photo. On Feb. 24, 1919, during Pres. Wilson's visit to Boston, suffragists of the National Woman's Party demonstrated at the State House and burned the President's speech at the Parkman Bandstand. As many as 25 suffragists were arrested, and 19 were jailed.
"Boston Common. 1918, showing Tremont and Park Sts," 1918, Boston Pictorial Archive, Boston Public Library, Digital Commonwealth, https://ark.digitalcommonwealth.org/ark:/50959/nv935h825
In this 1905 photo, Park Street is at the left, and the buildings have many awnings. Tremont Street runs across the photo. 167 Tremont, BESAGG headquarters from 1916 to 1918, may be the light colored, narrow five-story building at almost far right.
Marr, Thomas E., -1910. "Boston Common and Tremont Street," 1905, Boston Pictorial Archive, Boston Public Library, Digital Commonwealth, https://ark.digitalcommonwealth.org/ark:/50959/nv935h92d
Other old images of Park Street include this one. Others tend to focus on the Amory-Ticknor house at 9 Park Street. See one from 1886 here, one undated, three from 1934 here, here, and here. 1935 HABS photo, and c1935 HABS survey. A book about Park Street has two images of Park Street, and fascinating history, but no mention of suffrage activity. Robert Means Lawrence, Old Park Street and its Vicinity (Boston: Houghton Mifflin Company, 1922), frontispiece and 52, here. The Massachusetts Historical Society has more photos of Park Street. See also Derek Strahan, "Beacon and Park Streets, Boston," October 19, 2015, Lost New England blog, here.