In the routine of duty some of the officers of the Army and Navy who first established temporary governments in California and New Mexico have been succeeded in command by other officers, upon whom light duties devolved; and the agents employed or designated by them to conduct the temporary governments have also, in some instances, been superseded by others.  Such appointments for temporary civil duty during our military occupation were made by the officers in command in the conquered territories, respectively.

On the conclusion and exchange of ratifications of a treaty of peace with Mexico, which was proclaimed on the 4th instant, these temporary governments necessarily ceased to exist.  In the instructions to establish a temporary government over New Mexico, no distinction was made between that and the other Provinces of Mexico which might be conquered and held in our military occupation.

The Province of New Mexico, according to its ancient boundaries, as claimed by Mexico, lies on both sides of the Rio Grande.  That part of it on the east of that river was in dispute when the war between the United States and Mexico commenced.  Texas, by a successful revolution in April, 1836, achieved, and subsequently maintained, her independence.  By an act of the Congress of Texas passed in December, 1836, her western boundary was declared to be the Rio Grande from its mouth to its source, and thence due north to the forty-second degree of north latitude.  Though the Republic of Texas, by many acts of sovereignty which she asserted and exercised, some of which were stated in my annual message of December, 1846, had established her clear title to the country west of the Nueces, and bordering upon that part of the Rio Grande which lies below the Province of New Mexico, she had never conquered or reduced to actual possession and brought under her Government and laws that part of New Mexico lying east of the Rio Grande, which she claimed to be within her limits.  On the breaking out of the war we found Mexico in possession of this disputed territory.  As our Army approached Sante Fe (the capital of New Mexico) it was found to be held by a governor under Mexican authority, with an armed force collected to resist our advance.  The inhabitants were Mexicans, acknowledging allegiance to Mexico.  The boundary in dispute was the line between the two countries engaged in actual war, and the settlement of it of necessity depended on a treaty of peace.  Finding the Mexican authorities and people in possession, our forces conquered them, and extended military rule over them and the territory which they actually occupied, in lieu of the sovereignty which was displaced.  It was not possible to disturb or change the practical boundary line in the midst of the war, when no negotiation for its adjustment could be opened, and when Texas was not present, by her constituted authorities, to establish and maintain government over a hostile Mexican population who acknowledged no allegiance to her.  There was, therefore, no alternative left but to establish and maintain military rule during the war over the conquered people in the disputed territory who had submitted to our arms, or to forbear the exercise of our belligerent rights and leave them in a state of anarchy and without control.