Deseret was to have boundaries as follows:
Commencing at the 33d parallel of north latitude, where it crosses the
108th deg. of longitude west of Greenwich; thence running south and west
to the boundary of Mexico; thence west to and down the main channel of
the Gila River (or the northern line of Mexico), and on the northern
boundary of Lower California to the Pacific Ocean; thence along the coast
northwesterly to 118 degrees, 30 minutes of west longitude; thence north
to where said line intersects the dividing ridge of the Sierra Nevada
Mountains; thence north along the summit of the Sierra Nevada Mountains
to the dividing range of mountains that separate the waters flowing into
the Columbia from the waters running into the Great Basin; thence
easterly along the dividing range of mountains that separate said waters
flowing into the Columbia River on the north, from the waters flowing
into the Great Basin on the south, to the summit of the Wind River chain
of mountains; thence southeast and south by the dividing range of
mountains that separate the waters flowing into the Gulf of Mexico from
the waters flowing into the Gulf of California, to the place of
beginning, as set forth in a map drawn by Charles Preuss, and published
by order of the Senate of the United States in 1848.
This description needs some explanation. The point of beginning, as set
forth, was at the headwaters of the Gila River near the Mexican line,
which then, and until the Gadsden Purchase in 1854, followed down the
Gila River to the Colorado. At that time the boundary between Upper and
Lower California had been established to the point below San Diego, which
thus became included within the territory claimed. Here, naturally, there
was inclusion of practically all Southern California to a point near
Santa Barbara. Thence the line ran northward and inland to the summit of
the Sierra Nevadas, not far from Mt. Whitney. It followed the Sierra
Nevadas to the northwestward, well within the present California line, up
into northwestern Nevada, thence eastward through southern Idaho and
Wyoming to about South Pass, where the eastern line was taken up
southward, along the summit of the Rockies to the point of beginning. So,
there was general inclusion of that part of California lying east of the
Sierras, of all southern California, all Nevada and Utah, the southern
portions of Oregon and Idaho, southwestern Wyoming, western Colorado, not
reaching as far as Denver, western New Mexico and all Arizona north of
the Gila.
There can be no doubt that the region embraced, probably too large for a
State under modern conditions, at that time was as logical a division as
could have been made, considering the semi-arid climatic conditions,
natural boundaries, generally by great mountain ranges, a single
watershed, that of the Colorado River, and, in addition to all these, the
highway outlet to the Pacific Ocean, to the southwest, through a country
where the mountains broke away, along the course of the Colorado, even
then demonstrated the most feasible route from Great Salt Lake City to
the ocean.