JEC Frontier Timeline By Miracline Jan 1, 1846 Treaty of 1846 Treaty between American and Britain over the Oregon Territory Apr 2, 1848 Mexican cession Jan 1, 1849 Kindred Spirits by Asher Brown Durand Oil on Canvas Period: Jan 1, 1863 to May 10, 1869 Construction of the Transcontinental Railroad A 1,907 mile (3,069 km) contiguous railroad line Jan 1, 1866 Twilight on the Plains, Platte River, Colorado by Worthington Whittredge Oil on canvas May 10, 1869 The First Transcontinental Railroad Mar 1, 1872 Yellowstone National Park was created. Aug 1, 1876 Colorado became the 38th state. Jan 1, 1878 Green River, Wyoming by Thomas Moran Oil on Panel
