Guernsey was born in 1839 in Calais, Vermont, to Gilman and Clotina (Southwick) Guernsey. He served in the Civil War, after which he relocated to Montpelier. After working as a builder, he established himself as an architect. He would go on to become the leading architect in Vermont.
In 1897, he was elected as Montpelier's third mayor. He died of tuberculosis at home in 1900.
Many of Guernsey's buildings contribute to historic districts on the National Register of Historic Places, in addition to one individual structure. In 2013, a book called Vermont's Elusive Architect: George H. Guernsey was published by the Bethel Historical Society, where Guernsey had designed the town hall. The book found Guernsey to be one of the most influential 19th century architects in Vermont.
1875 - French's Block, 32 Main St, Montpelier, Vermont1875 - Union Block, 26 State St, Montpelier, VermontBurned in 1914.1878 - Universalist Church (former), 201 Bridge St, Richmond, Vermont1879 - Walton Block, 17 State St, Montpelier, Vermont1880 - George H. Guernsey House, 68 E State St, Montpelier, VermontThe architect's own residence.1883 - Blanchard Block, 73 Main St, Montpelier, Vermont1884 - St. Charles R. C. Church, 31 Cherry Hill St, Bellows Falls, Vermont1885 - Holy Angels R. C. Church, 246 Lake St, St. Albans, Vermont1886 - Notre Dame de Victoire R. C. Church, Main & Winter Sts, St. Johnsbury, VermontBurned in 1966.1887 - Barton M. E. Church (former), Church St, Barton, Vermont1888 - Christ M. E. (St. John's) Church, 135 Main St, Lancaster, New Hampshire1888 - St. Francis de Sales R. C. Church, 238 Main St, Bennington, Vermont1889 - Edward Dewey House, 128 State St, Montpelier, Vermont1890 - John W. Burgess House (Redstone), 26 Terrace St, Montpelier, Vermont1891 - Bethel Town Hall, 134 S Main St, Bethel, Vermont1891 - Dodge Hall, Norwich University, Northfield, VermontDemolished.1891 - Immaculate Heart of Mary R. C. Church, 18 Lincoln Ave, Rutland, Vermont1891 - United Baptist Church, 23 Park St, Lakeport, New Hampshire1891 - St. Thomas R. C. Church, 6 Green St, Underhill, Vermont1892 - Ludlow Baptist Church, 99 Main St, Ludlow, Vermont1892 - St. Augustine R. C. Church, 16 Barre St, Montpelier, Vermont1892 - Whiting Library, 117 Main St, Chester, Vermont1893 - Bradford Academy, 172 N Main St, Bradford, Vermont1893 - Debevoise Hall, Vermont Law School, South Royalton, Vermont1893 - Plymouth Congregational Church (Remodeling), 4 Post Office Sq, Plymouth, New HampshireBurned.1894 - Brownell Block, 20 Main St, Essex Junction, Vermont1895 - Hotel Barton, 569 Main St, Barton, VermontBurned.
