Sidney Drake Jackman, farmer, educator, Confederate officer, and state representative, was born in Jessamine County, Kentucky, on March 7, 1826, the son of Thomas and Mary (Drake) Jackman. The Jackman family moved to Howard County, Missouri, around 1830. Here Jackman received a basic education. Jackman was living in Boone County by the late 1840s, teaching school and farming. Here on February 18, 1849, he married Martha Rachael Slavin; this couple had four sons and two daughters. Shortly after this marriage Jackman returned with his family to Howard County and stayed there until 1855 when the family relocated near the Kansas border at Papinville, Bates County, Missouri. During this time Jackman continued to work as a farmer and schoolteacher. At this last location Jackman organized and led local militias to counter "Jayhawker" and outlaw raids from Kansas. In 1860 Jackman moved his family back into the interior of Missouri to avoid these depredations.
When the Civil War began the following year, Jackman entered on the side of the Confederacy. He served for a time as a captain in regular Confederate Missouri units before organizing and leading his own body of guerilla troops known as Jackman's Missouri Cavalry. Around 1864 he returned to regular duty, this time as colonel and commander of the Confederate Seventh Missouri Infantry Regiment. Just before the close of the war in the spring of 1865, Jackman was promoted to brigadier general and put in charge of troops in southern Missouri. In the meantime Federal troops had taken his family captive as retribution for his guerilla activities, transferring them first to St. Louis, and later to Natchez, Mississippi, and Alexandria, Louisiana. At the cessation of hostilities Brigadier General Jackman and a host of his troops refused to surrender and take the Federal loyalty oath, electing instead to flee to Mexico. Jackman reunited with his family in Shreveport, Louisiana, and proceeded with them toward Mexico by way of Texas. They arrived in San Marcos, Hays County, toward the end of 1865, and Jackman left his family there while he scouted the family's prospects in Mexico. Upon his return in 1867 Jackman settled his family on a homestead near Kyle, Hays County, and surrendered to Federal authorities in San Antonio. He was taken to New Orleans where he took the loyalty oath and was paroled.
Jackman returned to Hays County where he farmed and assumed a prominent role in community affairs. He and his wife helped establish First Christian Church, Disciples of Christ, and he was a trustee of Blanco Chapel Free School. In 1873 he won election as representative for District Twenty-seven—comprised of Guadalupe, Caldwell, Hays, and Gonzales counties—to the Fourteenth Texas Legislature. His wife Martha died in 1870; Jackman remarried to the widowed Cass (Kyle) Gains in 1875. This couple had two sons and two daughters. Jackman's final turn at public service came in 1885 when he received a presidential appointment as United States marshal for western Texas. Brig. Gen. Sidney Jackman died in Hays County on June 2, 1886, and was buried there at Kyle Cemetery.