Ephraim Gilman, Map of the United States Now Expanded Coast to Coast (1848)

This map by U.S. General Land Office principal draftsman Ephraim Gilman was produced at the behest of President James K. Polk to accompany his December 1848 addess to Congress. It shows that the 1840s had been a consequential decade for the expansion of the United States, stretching now from coast to coast after the 1845 annexation of Texas, the 1846 British cession of the Oregon Territory south of the 49th parallel (present-day Washington, Oregon, Idaho, and part of Montana), and the 1848 Mexican cession of present-day California, Nevada, Utah and parts of Colorado, Wyoming, Arizona, and New Mexico after the Mexican-American War. Despite the fact that Gilman was an experienced draftsman, the map has serious labeling errors, misspellings, and misplacements of major geographic features--mistakes that were likely a reflection of Polk's expansionist views and the haste with which the map was made rather than Gilman's cartographic skills. For example, Texas is smaller on the map than it should be, largely because Gilman used the flawed 1847 Disturnell map that was referenced in the Treaty of Guadalupe Hidalgo to draw his map. Notably different from Disturnell's map though, is the clear boundary between Texas and the territory of New Mexico, with Santa Fe unquestionably within the boundaries of Texas, which seems to be a message from Polk about his stance on a long-standing boundary dispute between Mexico and Texas. Also politically significant is a line drawn from the southern boundary of Missouri to the Pacific Ocean--a rendering of Polk's policy suggestion to extend the line of the Missouri Compromise of 1820 to the Pacific Ocean, thereby extending slavery to any territories south of the 36º 30' line, rather than admitting California as a free state. This was Polk's answer to the firestorm of controversy that erupted in response to the Wilmot Proviso, suggesting that slavery be banned from all territories acquired from the Mexican-American War.  However, Gilman mistakenly drew the line at 39º 30'.