Understanding the #UnitedStatesofAmerica The Treaty of Guadalupe Hidalgo - Article VI

The Treaty of Guadalupe Hidalgo

ARTICLE VI

The vessels and citizens of the United States shall, in all time, have a free and uninterrupted passage by the Gulf of California, and by the river Colorado below its confluence with the Gila, to and from their possessions situated north of the boundary line defined in the preceding article; it being understood that this passage is to be by navigating the Gulf of California and the river Colorado, and not by land, without the express consent of the Mexican Government. 

If, by the examinations which may be made, it should be ascertained to be practicable and advantageous to construct a road, canal, or railway, which should in whole or in part run upon the river Gila, or upon its right or its left bank, within the space of one marine league from either margin of the river, the Governments of both republics will form an agreement regarding its construction, in order that it may serve equally for the use and advantage of both countries

You can read the Treaty of Guadalupe Hidalgo for yourself here (an 11-page PDF) - https://www.nps.gov/common/uploads/teachers/lessonplans/Treaty-of-Guadalupe-Hidalgo-Transcript.pdf