In the mid 19th century, the United States pressured Mexico for transit rights across the Isthmus of Tehuantepec, with the aim of building a road, railway or canal for the purpose of connecting the Atlantic and Pacific Oceans for trade. Pressure was greatest during the Mexican–American War, when these transit rights were part of the first attempts at talks to end the war. However, this was not included in the Treaty of Guadalupe Hidalgo. During negotiations for the Gadsden Purchase, the issue came up again but transit rights were again denied. Despite strong interests in the area, the U.S. Army never invaded Tehuantepec, even though troops had gone as far south as southern Veracruz. However, the war drained the south of the country of soldiers and lessened control from Mexico City. As a result, the Isthmus area rebelled against rule from the city of Oaxaca. In 1850, the first plan to separate the Tehuantepec area from Oaxaca took shape. The result was regaining of a certain amount of autonomy. A second attempt took place in 1853.