He was an early resident of Baker City in Eastern Packwood received two years of formal education and later moved to Springfield, Illinois where he knew future United States President Abraham Lincoln. In 1848 he enlisted in the United States. Army with Company Bachelor of the United States. Mounted Rifles. The following year Packwood and the company were sent to the newly created Territory and stationed at Fort Vancouver.
Packwood went to California when gold was discovered there, returning to in 1851 where he was transferred to Portuguese Orford, to fight Native American uprisings.
In 1853 he was discharged from the Army and became a gold miner for several years. In 1855, Packwood served as captain of the Coquille Guards during the Rogue River Wars against Native Americans in Southern In 1857, he represented Curry County in southwestern at the Constitutional Convention that met in Salem during August and September, and framed a constitution in anticipation of becoming a state.
He was the youngest of the delegates at the convention. Packwood then moved east of the Cascade Mountains to Eastern where he was involved with establishing the town of Auburn in 1862.
Auburn was a gold-mining boomtown that was briefly the county seat of Baker County, and Packwood helped plat the town.
There he served as the first school superintendent of Baker County in 1862. During the 1864 presidential election he campaigned for Lincoln in that county. Soon after, he was responsible for another Baker County town receiving the name of Sparta.
In that town he and his family built and operated a boarding house until 1867.
In later years Packwood mined, was an assistant postmaster, clerk for Baker City, and a police judge before retiring in 1910. He is the great-grandfather of former United States Senator Robert Packwood.
William Henderson Packwood died on September 21, 1917, in Baker City with interment at Mount Hope Cemetery.
He was the last living member of the constitutional convention at his death.