After Cartee arrived in Oregon City, he opened a surveying and engineering business. The early 1850s were a good time to be a surveyor in Oregon since settlers attempting to secure property rights under the new
Donation Land Claim Act needed their land accurately surveyed in order to file their claims. In addition, as a well-educated professional, Cartee quickly became a respected member of the Oregon City community, which was the seat of government for the Oregon Territory at that time. In 1853, Cartee was elected as a delegate to the Oregon Territory's Democratic convention, representing
Clackamas County. He served on the resolutions committee during the convention. Following the territorial convention, Cartee attended the Clackamas County Democratic convention, where he was selected as one of three Democratic nominees for a Clackamas County seat in Oregon's territorial House of Representatives. The other two Democratic nominees were
F. C. Cason and
B. B. Jackson. Cartee and his two fellow Democrats were elected to the three Clackamas County seats in the Oregon House of Representatives. He took his seat in the Oregon House on December 5, 1853. He served through the 1853 session which ended on February 2, 1854. During the session, Cartee was appointed to the joint code committee, responsible for proposing new public laws. Cartee ran for re-election in 1854. Once again, the Clackamas County's Democratic convention selected him as one of three candidates nominated to run for an Oregon House seat representing the county. The other two Democratic nominees were
William A. Starkweather and J. Guthrie. Cartee and Starkweather won seats, but the third Clackamas County seat was won to
Asa Lovejoy, a
Whig Party candidate. When the House was organized, Cartee was elected Speaker of the House. He served as speaker through the 1854 session, which ended on February 1, 1855. During the session, the legislature created
Wasco County which at that time included all of
Eastern Oregon. The legislature also combined eastern
Washington County and a northern section of Clackamas County to create
Multnomah County. A bill was introduced that would have asked Oregon voters to approve holding a convention to draft a constitution, a mandatory first step in the process of seeking statehood. However, that bill did not pass. Between legislature sessions, Cartee continued his survey work. In 1854, he was awarded a government contract to survey from
Camas, Washington south to
Estacada, Oregon. During that time, he trained several assistant surveyors including
David P. Thompson, who was later appointed
governor of the Idaho Territory. Sometime after leaving the legislature, Cartee quit the Democratic Party and joined the newly formed
Republican Party. During the
American Civil War, he was a strong and active supporter of the
Union cause, encouraging Oregon voters to support pro-Union candidates regardless of their party affiliation. In 1862, he was hired by the
Oregon Steam Navigation Company as chief engineer responsible for constructing a 14-mile portage railroad along the south shore of the
Columbia River. The railroad was necessary to bypassing the river's unnavigable rapids between
Celilo Falls and The Dalles. This short line was the first railroad built in Oregon. His wife, Mary, died in The Dalles in 1862 while Cartee was away from home working on the railroad. Cartee never remarried. In 1863, he moved with his children to
Boise City in the Idaho Territory. When his son was fourteen-years-old, Cartee sent him to The Dalles to recover Mary's body and transport it to Boise for re-burial. == Idaho Territory ==