Bartlett returned to Providence in 1850. He then traveled to Washington D.C., intending to request the position of ambassador to Denmark. Instead he was offered the position of
United States Boundary Commissioner responsible for surveying the boundary between the United States and
Mexico. This required him to form a group to travel throughout the
Southwest. He did resist some inappropriate requests, daring to reject the recommendation of one Thomas W. Jones by
Henry Clay and nine other US Senators, pointing out that Jones was "a hanger-on in Washington and all wanted him out of the way". Some group members were more useful; in addition to the professional surveyors, there were four botanists and four zoologists who made significant contributions. Some were at least decorative; the painter
Henry Cheever Pratt contributed thirty plates to Bartlett's
A Personal Narrative of Explorations and Incidents in Texas, New Mexico, California, Sonora and Chihuahua (2 vols, 1854), published after Bartlett was superseded by
another commissioner. It contains much valuable scientific and historical material concerning the area. Bartlett collected word lists from many of the Native Americans who he met. The autoethnonym of the
Seri people of northwestern Mexico, Comcaac (which he wrote as "komkak"), was first recorded by Bartlett during a short visit to the area in early 1852. The word was included in the list of approximately 180 words that Bartlett archived in the
Bureau of American Ethnology (now part of the
National Anthropological Archives, housed at the
Smithsonian Institution). He remained Boundary Commissioner from 1850 to 1853, when the Whig Party lost power upon the accession of
President Franklin Pierce. ==Secretary of State for Rhode Island, librarian==