The history of the First Congregational Church of Willimantic (199 Valley Street) is provided in Richard M. Bayles’ History of Windham County, Connecticut (1889):
The religious sentiment of Willimantic is now represented by six churches, viz., Congregational, Methodist, Baptist, Roman Catholic, Protestant Episcopal and Spiritualist. These have all been built up here since the year 1827. Up to the close of that year there was no church nearer than Windham Centre, nor any stated meetings except such as were held in a school house or in private houses. In the year mentioned a few persons here applied to the directors of the Connecticut Domestic Missionary Society for a minister. [. . .]
January 22d, 1828, an ecclesiastical council was called, of which Doctor Samuel Nott, of Franklin, was chosen moderator, and this council organized the First Congregational church of Willimantic. [. . .]
A church edifice was immediately erected, and was dedicated October 17th, 1828, Doctor Joel Hawes preaching the sermon. This was the first house of worship in the place. The expense of building it was a burden from which those who undertook it delivered themselves only after a determined struggle. The present society was formed soon after the church was built. [. . .] In 1843 the house of worship was considerably enlarged. [. . .]
On the acceptance of the call of Reverend Horace Winslow, the question of a new house of worship was earnestly advocated, and on February 24th, 1869, the society resolved to proceed to the work, and accordingly appointed a building committee composed of John Tracy, Allen Lincoln, William C. Jillson and the pastor elect. In July of that year the corner stone was laid, and in one year from that time the main edifice was dedicated to the worship of God. The expenses of this enterprise were provided for in various ways. To begin with, the society had from subscriptions and the sale of the old house $19,578. This fund was steadily increased by special efforts, so that when the main portion of the building was completed the debt was only a little over $9,000. In May, 1871, the chapel was completed and dedicated to the service of God. In about a year from that time it was proposed to pay off the whole debt of the society, which amounted then to $12,600. This amount was raised by the 1st of October, 1872. The whole cost of church, grounds, chapel, furniture, organ and all, amounted to $46,700, and it had all been paid, so that the society was free from debt. A service of praise and gratulation was held in view of the auspicious financial condition. Since then money has been raised and the chapel and adjoining rooms have been painted, carpeted and seated. The size of the main edifice on the ground is one hundred by sixty-three feet, and the chapel addition and adjoining room is ninety by thirty-six feet.