Seth Eastman, artist and career military officer, was born in Brunswick, Maine, on January 24, 1808, the first child of Robert and Sarah Lee Eastman. In 1824 he entered the United States Military Academy at West Point. There he received his first lessons in technical draftsmanship from the French miniature painter and engraver Thomas Gimbrede and honed his skills in drawing landscape, topography, and the human figure. He graduated twenty-second in his class and received his commission on July 1, 1829. His first assignment was to Fort Crawford at Prairie du Chien, Wisconsin. In 1830 he was transferred to Fort Snelling, Minnesota, where he was assigned to topographical duty. He returned to West Point in 1833 and held the position of assistant teacher of drawing until 1840. His Treatise on Topographical Drawing, published in 1837, was used as a textbook at West Point. During this time he studied landscape painting under Charles Robert Leslie and Robert W. Weir and became known as a minor painter of the Hudson River School. His landscape drawings show the influence of the romantic landscape style of early nineteenth-century Europe. Between 1836 and 1841 he exhibited his work at the National Academy of Design and the Apollo Gallery in New York City, and in 1838 the NAD presented him a diploma as an "Honorary Member Amateur." While at West Point Eastman met Mary Henderson, daughter of the assistant surgeon at the academy. They married in 1835 and had four boys and a girl.
In 1840 Eastman participated in the Seminole War, and produced a number of sketches of the Seminole Indians. He returned to Fort Snelling in 1841 and remained there until 1848. His interest piqued by his contact with the Seminoles in Florida, he made hundreds of pencil and watercolor studies and oils of the Indians of the area (chiefly Dakotas and Chippewas). His straightforward representations of Indians engaged in everyday activities-chasing buffalo, gathering wild rice, preparing skins for lodges and clothes-established his reputation as a chronicler of Indian life. His wife shared his interest in Indians and wrote several books, many of them illustrated by her husband, that contained Indian legends and descriptions of scenes around the fort.
Against his wishes, Eastman was ordered to Texas in 1848 to protect settlers against Indian raids and to help establish a line of frontier forts. He kept a detailed sketchbook of his journey down the Mississippi River and his tour of duty in Texas. He also kept a journal and map that record a march in August 1849 from the Leona River to San Antonio and then on to the Nueces River. The sketchbook consists of nearly 150 drawings; more than seventy are scenes of his journey down the Mississippi, and sixty-five are Texas scenes. Five drawings record the approach to Matagorda Bay and the landing at Indian Point, and ten illustrate the journey up the river valley to Seguin and San Antonio. His nine drawings of San Antonio include the most detailed and accurate scenes of the Alamo; missions San José, Concepción, and San Juan; the old San Fernando Church (now San Fernando de Bexar Cathedral); and overall views of the city from that period. Although he was primarily an Indian painter, in Texas Eastman was captivated by the Hill Country landscape. In the fifteen sketchbook views of the two-year-old settlement of Fredericksburg, live oaks and the activities of the German colonists predominate. Indians appear in these sketches only occasionally as background figures. Other sketches include views of the Leona and Frio rivers, military camps in those areas, and various landscape scenes from around San Antonio. In addition to the sixty-five scenes of Texas in his sketchbook, Eastman did a number of watercolor sketches and at least one oil painting.
In 1849 he was sent to Washington, D.C., where he was commissioned to do the illustrations for Henry Rowe Schoolcraft's Historical and Statistical Information Respecting the History, Condition and Prospects of the Indian Tribes of the United States, published in six volumes between 1852 and 1857. In 1855 he was sent back to Texas to command regiments at Fort Duncan and Fort Chadbourne. Eastman is not known to have done any drawings or paintings during his second stay in Texas. During the early part of the Civil War he served as mustering and disbursing officer for Maine and New Hampshire, and he became the military governor of Cincinnati, Ohio, in 1863. Later that year he was retired from active duty at the rank of lieutenant colonel. He was brevetted brigadier general in 1866 and in 1867 served on modified assignment in Washington, D.C., where he was commissioned to paint scenes of American Indians and United States forts for the Capitol.
Eastman died in Washington on August 31, 1875. In 1947 his great-granddaughter, Anna Jayne Moebs, approached San Antonio businessman and collector Paul Adams with the intent of selling Eastman's sketchbook. Adams arranged for B. B. McGimsey, general manager of the San Antonio Brewing Association, to purchase the sketchbook and later discovered and bought the accompanying journal in a New York City bookstore. The sketchbook was donated to the Marion Koogler McNay Art Museum by the Pearl Brewing Company of San Antonio; the journal remained in the possession of Paul Adams. Eastman's work is also included in the collections of the Witte Museum in San Antonio, the Peabody Museum of Archeology and Ethnology, and the James Jerome Hill Reference Library in St. Paul, Minnesota.