The congregation was able to form in the aftermath of an 1843 decision to expand religious freedom in Connecticut. Prior to this year, Jews were forbidden from conducting public services or constructing synagogues. Connecticut's Jewish population was small, but by the mid-19th century, it was active enough to petition the Connecticut General Assembly for greater religious rights. The Assembly agreed to allow Jews freedom of worship, paving the way for the establishment of Jewish congregations and synagogues in Connecticut.
CBI's founding members were primarily German Jews who had immigrated to the United States during the 19th century. As of 1877, around the time of the Charter Oak temple's construction, Connecticut's Jewish population is estimated at 1500 (Ransom, p. 8). This number would rise dramatically in the following decades, large numbers of Eastern European Jews also immigrated to the US.
The 1870s also saw considerable changes within the traditionally Orthodox congregation. Many members wished to adopt Reform practices (e.g. installation of a choir, acquisition of an organ, changes in worship and prayer books). Ultimately, CBI members in favor of Reform won out over those preferring Orthodox Judaism. In 1874, the community appointed Dr. Solomon Deutsch, a committed reformer, as its rabbi.
Two years later, the Charter Oak Synagogue opened its doors. This architecturally striking building was designed by George Keller in the Romanesque Revival style. Like Temple Emanu-El in New York City, Charter Oak Temple took inspiration from Berlin's New Synagogue on Oranienburgerstrasse. As the first purpose-built synagogue in Connecticut, Charter Oak temple would then go on to inspire the design and aesthetic of future Connecticut synagogues.