Before the Federal Government established the Armory in 1795, Springfield’s population consisted mostly of Congregationalists of British decent. In 1636, William Pynchon had led a group of twenty to forty people from Roxbury to Springfield and established a plantation. Through the Revolutionary War period, the demographics of the town had not changed much. Even as the Armory attracted more workers, the majority of them were not foreign born. The proportion of immigrants, mostly Irish, remained steady at around 20% through the Civil War. However, these immigrants seemed to be staying in town longer, and births to immigrant parents began to overtake native births.

By 1855, at least 2,223 Irish lived in the town. Many came to lay the new railroad tracks. After the tracks were laid, many became laborers on construction gangs. French-Canadians also began to arrive in the 1850s. Most worked in the textile mills of Indian Orchard. Germans, fleeing the German Revolution of 1848, came to Springfield as skilled craftsmen. Nativist hostilities, however, were strong in the 1850s when the people elected a mayor from the anti-immigrant, “Know-Nothing” party.

African Americans made up a very small portion of Springfield’s population in the early to mid-1800’s. According to the 1830 national census, there were 48 African Americans out of 6000 people in Springfield. A decade later, there were 101 out of 11,000 - an increase of 48 percent. In 1838, Springfield residents formed their first anti-slavery society, which included both black and white members. By 1850, the African-American population had doubled to over 200. The Springfield Armory was not known to have employed African-Americans during this period. African-Americans worked mostly in service sector and general labor jobs. By 1860, the Springfield African-American community had established the Sanford Street Church that later became the Free Congregational Church and known today as St. John’s.

The Armory had a strong influence on religious life in Springfield. Many of the workers who came to the Armory challenged the dominance of the Congregational Church. In 1816, Roswell Lee, the Superintendent of the Armory, asked the Federal Government to designate a chapel on Armory grounds because most of his workers were Episcopalians and had nowhere to worship. Within a few short years, the workforce included Baptists, Roman Catholics, and Universalists.

The Armory and surrounding industries played a role in creating greater diversity in Springfield.