The building was designed by Nathaniel Jeremiah Bradlee, constructed in a High Victorian Gothic style, and included ground-level retail.

All young men of good moral character, and claiming to believe in the truths of Christianity, without distinction of sect or party, were eligible as members of this society.

[citation needed] The report of 1871 shows the Union organized, with committees as follows: finance; lectures, classes, and entertainments; library; rooms; members; benevolent action; public worship and religious study.

In 1875, there were classes in book-keeping, German, French, parliamentary law, vocal music, astronomy, elocution, and Shakespeare; monthly socials were held, at which many of Boston's most cultured women were present; and a Christmas and New Year's festival was given to poor children.

The report for 1900 showed that the secular classes had grown in variety and attendance, that the library had 15,000 volumes, that the membership was 5,554, that religious services had been held every Sunday except during July and August, and that over $18,000 had been expended in drives, bay trips, and country visits for the poor.