IMPERIALISM AND INDEPENDENCE 89ethnographic interest in the mysterious native tribes
that were rumored to live in this area.
The expedition also convinced him that the Rocky
Mountains were the backbone of North America,
with headwaters of rivers that flowed eastward
and westward into two different oceans. The most
geographically accurate aspect of the map was the
depiction of the upper Colorado River Basin, as well
as the San Juan and Dolores rivers. On the map, the
San Juan River is marked “Rio de Nabajoo,” fed by
several tributaries to the north.
But there were also serious errors, most of which
grew out of Miera’s hope of finding a navigable river
flowing west from the Rocky Mountains through
the Great Basin to the Pacific Ocean. At upper left,
he asserted a large river flowing west from Lake
Timpanogos. Miera invested similar hope in the
Rio de S. Buenabentura to the east (later named
the Green River), which he believed would drain to
“Laguna de Miera” and the Pacific beyond.
Miera’s map influenced geographic knowledge
for decades, as is apparent in maps compiled by
Alexander von Humboldt and Zebulon Pike in about
- But perhaps just as intriguing is its diplomatic
influence. When the Americans completed the
Louisiana Purchase in 1803, they argued that the
southwestern border included all the land to the Rio
Grande, including much of present-day Texas. The
Spanish countered that the border lay much further
east, and used the topographic detail on this map to
demonstrate their superior knowledge of the terrain
and their historical rights to the region. That western
border of Louisiana Territory would remain contested
for years, first with Spain and later with Mexico. The
entire area mapped here became part of the United
States in 1848, though its rich and complex Spanish
and Mexican heritage endures.