Rev. Ithamar Pillsbury was the founder of the Andover Colony and the first pastor of the Andover Presbyterian Church of Henry County, Illinois. He was the youngest child of Deacon Joshua and Elizabeth Sawyer Pillsbury. The family moved to Canaan, New Hampshire in 1795, where his father was a Deacon in the Congregational Church. An older brother, Levi, was an ordained minister of the Congregational Church at Winchendon, Massachusetts. Ithamar enlisted in the War of 1812 and his life was spared one day; a musket ball grazed his head and killed the soldier behind him. His religious upbringing and this military experience inspired him to become a man of God. He entered the Union Academy in Plainfield, New Hampshire in 1815. Due to the lack of funds to continue his education, he had to break from his studies several times and do teaching jobs. In 1818, he entered Yale College. After graduation, he went to New York City to study Theology with Rev. Drs. Gardiner Spring and E. W. Baldwin. He married the widow of Captain Mix, of New Haven, a religious and accomplished lady of means, who helped him through college. In October, 1824, he became licensed to preach the gospel by the Presbytery of New York, and on June 19, 1825, he was ordained and was preaching at the Spring Church. In January 1826, he was working as an evangelist at the Female Society of Missions of Boston and worked among the mariners. In September, 1827, he stood in the pulpit at Smithtown, Long Island and became pastor there in 1830. He resigned in April, 1833 and started working at the American Sunday School Union and Educational Society. He began preaching at Sag Harbor for about a year, resigning in 1835. He felt a call to become a missionary out West. In the spring of 1835, he was appointed by the Presbytery of Long Island to become a Commissioner to the General Assembly, Pittsburg, Pennsylvania. After attending the Assembly sessions, he went on a tour of Illinois, with a plan to start a colony. He spent the summer in Illinois, returning to New York in September; he made a report of his observations and was able to organize the company of The New York Association with a capital $40,000 to be invested in the purchase of land in Illinois. He, with N. T. Pike and A. Slaughter left in October, 1835 for Illinois. They located and purchased twenty-two sections of land in Henry County; the town was named Andover, which Ithamar wanted as a commerical, educational and religious center of the colony. He travelled to New Hampshire and found a millwright to erect a saw and grist mill on the nearby Edwards River; it was in operation by the summer of 1836. Several families had arrived and a settlement began to appear, houses built, and sod broken for planting. For the remainder of his life, Rev. Pillsbury was linked with the West, especially with concerns of the growth and success of the Presbyterian Church. His wife, Nancy died at Long Island, New York on April 19, 1837. They did not have any children. On August 22, 1837, he officiated at the first recorded marriage in Henry County - that of Lewis Hurd and Miss Caroline Little of Wetherfield. On December 18, 1837, the Rev. Enoch Mead officiated at the marriage of Rev. Pillsbury and Caroline E. Miller, daughter of Dea James S. and Abigail Hallock Miller, who come to Andover from Long Island, New York. Ithamar and Caroline had ten children. A meeting on the Sabbath, December 10, 1837 was held at the home of Rev. Pillsbury, to organize the Andover Presbyterian Church; 18 persons united with the church, 12 of whom brought letters from other churches and 3 united on profession. They met for public worship in the school houses or residences of members, usually at Rev. Pillsbury's home. He would walk or ride horseback from Andover to Kewanee on the fourth Sunday of each month, to take care of the villagers' religious needs. There were no bridges, so he would have to wade or swim across streams and rivers to minister at the different settlements. In 1850, Ithamar accepted a call to Princeton, Bureau County, Illinois. In 1864, he became President of McConough County College and pastor of the Presbyterian Church at Macomb, Illinois. In 1856, the Presbyterian Church at Andover was built at the cost of $3,000. In 1860, Rev. Pillsbury returned to Andover, as pastor of the church he organized some 22 years earlier.
The New York Association, of which he was the leader, with Elihu Townsend and Edward Mix, donated the land for the Andover Presbyterian Cemetery.