In 1843, Nesmith arrived in Oregon where he studied law and was admitted to the bar before being selected to serve as Supreme Judge of the Provisional Government of Oregon in 1845.
He finished his term in 1846 and moved to Polk County where he took a land claim, began farming, and married Pauline Goff on June 21, with whom he would have seven children.
In 1847, he was elected to the Provisional Legislature of Oregon from Polk County, and served briefly in the 1848 session before resigning.

Nesmith next served as a captain during the Cayuse War against Native Americans in Eastern Oregon from 1847 to 1848.
When news of the California Gold Rush reached the Willamette Valley in 1848, he traveled south to the gold fields, remaining until 1849.
In 1849, he returned to Polk County where he purchased a flour mill on Rickreall Creek near the county seat of Dallas.
There Nesmith engaged in agricultural pursuits in the community that was for a time named after him, as well as stock raising.

He again was a captain in the militia forces during the Rogue River War in 1853 and the Yakima Indian War in 1855.
Between the two wars he was the United States Marshal for the Oregon Territory, replacing Joseph Meek.
From 1857 to 1859 he was the Superintendent of Indian Affairs for Oregon and Washington Territories.

As Superintendent of Indian Affairs, Nesmith was aggressive against American Indians on Oregon's south coast, and once stated to Commissioner of Indian Affairs George Manypenny that the extermination of the Chetco people "would occasion no regrets at this office."
In 1843, Nesmith arrived in Oregon where he studied law and was admitted to the bar before being selected to serve as Supreme Judge of the Provisional Government of Oregon in 1845. He finished his term in 1846 and moved to Polk County where he took a land claim, began farming, and married Pauline Goff on June 21, with whom he would have seven children. In 1847, he was elected to the Provisional Legislature of Oregon from Polk County, and served briefly in the 1848 session before resigning.
Nesmith next served as a captain during the Cayuse War against Native Americans in Eastern Oregon from 1847 to 1848. When news of the California Gold Rush reached the Willamette Valley in 1848, he traveled south to the gold fields, remaining until 1849. In 1849, he returned to Polk County where he purchased a flour mill on Rickreall Creek near the county seat of Dallas. There Nesmith engaged in agricultural pursuits in the community that was for a time named after him, as well as stock raising.
He again was a captain in the militia forces during the Rogue River War in 1853 and the Yakima Indian War in 1855. Between the two wars he was the United States Marshal for the Oregon Territory, replacing Joseph Meek. From 1857 to 1859 he was the Superintendent of Indian Affairs for Oregon and Washington Territories.
As Superintendent of Indian Affairs, Nesmith was aggressive against American Indians on Oregon's south coast, and once stated to Commissioner of Indian Affairs George Manypenny that the extermination of the Chetco people "would occasion no regrets at this office."
James Nesmith