The California-Nevada Border War

Unidentified woman with surveyor Col. Alexey Von Schmidt at the 1872 border monument. It was later determined to be too far east. | Courtesy Nevada Historical Society

After the United States victory in the Mexican-American War (1846-1848), both countries signed a treaty giving the U.S. nearly half of Mexico’s original sovereign territory. When the question of California’s geographical size and official borders came up at the state’s first Constitutional Convention in October 1849, there were two main options considered. One called for including all of what Mexicans called Alta (Upper) California, an enormous chunk of land that extended from the Pacific Ocean east all the way to the Rocky Mountains and north to the 42nd parallel.

Read Mark’s four-part series on the Mexican-American War
Read Marks’ three-part series on Tahoe’s Water Wars

Many of the delegates, however, preferred a more manageable border near the Sierra Nevada, for both political and practical reasons. The possibility of a large state later being politically carved into slave territories was one serious concern. Others pointed out it would be a mistake to incorporate land where the Church of Latter-Day Saints had established its home base without the Mormons having representation at the convention. Among those pushing for a boundary near the Sierra Range was none other than the legendary topographical engineer, John C. Frémont, credited as the first Euro-American, along with his cartographer Charles Preuss, to see Lake Tahoe.

A Supreme Court ruling told each state to accept the current border, which Nevada quickly agreed to because of the high likelihood that the boundary … would strand the state’s casinos in California.

Frémont was a staunch abolitionist and a strong proponent of California entering the Union as a free state, not a slave state. Considering that Frémont had already seen Lake Tahoe — he named it Lake Bonpland —he probably assumed that Big Blue would be included within California.

On Oct. 11, 1849, James M. Jones, the youngest delegate at the convention, suggested an eastern border based on longitude and latitude, not geography. The delegate himself had not been to the mountains when he made his suggestion and despite his lack of surveying experience, the convention submitted to Congress an eastern border based on an imaginary grid, not the ground. This ill-conceived action caused headaches and confusion for Nevada and the federal government for more than a century. Bi-state water rights issues on the Truckee River continue to this day (read “Tahoe’s Water Wars” at

Two of California’s boundaries were already fixed: the Pacific Coast and the 42nd degree latitude for the northern border based on an earlier agreement incorporated into the Oregon Territory treaty when Great Britain relinquished all claims to the present-day Pacific Northwest. California’s southern state line would be run down the middle of the Colorado River and then along the 35th parallel on the border with Mexico, but it was the eastern boundary that gave everyone fits.

The northeast point of the state was established at the intersection of the 42nd parallel and 120th degree longitude; then “… running south along the 120th degree longitude until it intersects the 39th degree parallel [an intersection that falls within Lake Tahoe]; thence running in a straight line in a southeasterly direction to the Colorado River.”

Jones description placed Lake Tahoe and its water system — which flows into Nevada and the Great Basin, not the Pacific Ocean — directly in the crosshairs of dispute and disagreement between the Golden and Silver states. The first effort to mark the state’s eastern boundary was conducted in Placerville in 1855 by Surveyor General William Eddy. About all he was able to prove was that Carson Valley was in Utah Territory, not California.

Several other rough surveys were made, including the Houghton-Ives in 1863, which found that only two-thirds of Lake Tahoe fell within the new border. More surveys were undertaken and each found discrepancies with previous work. In 1872, the federal government hired astronomer and surveyor Alexey Von Schmidt to improve the results. This was the same Von Schmidt who proposed damming the Truckee River at Olympic Valley to send Tahoe water to San Francisco

Part of the challenge for these early surveyors — besides rugged topography, hostile Indians, lack of funding and an aggressive time schedule — was the difficulty of locating geographic coordinates, especially longitude. Of the two coordinates, latitude is the easiest to determine using astronomical observations and scientific instruments, but longitude is a function of time based on global meridians in relation to Greenwich, England.

At the 39th degree latitude (Lake Tahoe), a clock error of only one second would cause a surveyor to post his longitude marker nearly a quarter of a mile out of position. Von Schmidt faced challenges similar to his predecessors, but he had an important advantage when it came to determining longitude. By 1872, accurate time signals could be transmitted by telegraph from San Francisco. The wires followed the transcontinental railroad tracks and crossed the border near Verdi, Nev.

In addition to the technological challenges, Nevada caused more problems when it passed the Organic Act. Instead of simply recognizing California’s existing eastern border as its western margin, this act demanded California give up any land associated with waters that “did not flow into the Pacific.” The congressional acts that created Nevada Territory (1861) and the State of Nevada (1864) provided for a western boundary at the Sierra Nevada Crest if the California state legislature would agree to change its existing boundary from the 120th parallel. The Golden State, however, declined to relinquish any territory, particularly its portion of Lake Tahoe which is located east of the Sierra Crest.

Over the next half century, the boundary line moved back and forth multiple times. In 1868, the Clarence King survey moved the border north of Truckee 2 miles to the west. In 1873, Von Schmidt’s work pushed the line at North Lake Tahoe too far east. In 1893, another survey took a half-mile of land from Nevada at South Lake Tahoe and added a half-mile to California on the North Shore.

As recently as 1977, California sued Nevada over the border location and in 1985 Congress cleared title to 11,000 disputed acres. A Supreme Court ruling told each state to accept the current border, which Nevada quickly agreed to because of the high likelihood that the boundary at Lake Tahoe was too far west and a realignment east based on modern surveying tools such as GPS would strand the state’s casinos in California.

A hydrological border along the Sierra Crest would have mitigated many of the controversial issues of watershed management along the eastern Sierra Front, with Nevada having control over vital water sources emanating from the “California Mountains.” Fortunately, bi-state agreements and federal decrees have solved many of the problems associated with a state boundary that does not take into account important physical features like streams, lakes and rivers.