Fortification Rock, once a landmark hill on the

Colorado River The Colorado River ( es, Río Colorado) is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and northern Mexico. The river drains an expansive, arid drainage basin, watershed that encompasses parts of ...

before it was inundated, now known as Rock Island, southernmost and tallest of the Boulder Islands in

Lake Mead Lake Mead is a reservoir formed by the Hoover Dam on the Colorado River in the Southwestern United States. It is located in the states of Nevada and Arizona, east of Las Vegas. It is the largest reservoir in the US in terms of water capacity. L ...

Clark County, Nevada Clark County is located in the U.S. state of Nevada. As of the 2020 census, the population was 2,265,461. Most of the county population resides in the Las Vegas Census County Divisions, which hold 1,771,945 people as of the 2010 Census, across ...

. It has an elevation of 1284 feet. Fortification Rock appears on the 1861 Geological Map No. 1; Rio Colorado of the West, explored by 1st Lieut.

Joseph C. Ives Joseph Christmas Ives (25 December 1829 – 12 November 1868) was an American soldier, botanist, and an explorer of the Colorado River in 1858. Biography Ives was born in New York City on Christmas Day, 1829. He graduated from Bowdoin College ...

, which shows Fortification Rock, Ives Camp #59 and the course of the Colorado River from its mouth on the

Gulf of California The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja Ca ...

Las Vegas Wash Las Vegas Wash is a 12-mile-long channel (an Arroyo (creek), "arroyo" or "wash") which feeds most of the Las Vegas Valley's excess water into Lake Mead. The wash is sometimes called an ''urban river'', and it exists in its present capacity because ...

and the location of its features and other expedition camps along the way. Geological Map No. 1. Prepared by J.S. Newberry, M.D. Geologist to the Expedition. Explorations and Surveys. War Department. Map No. 1. Rio Colorado of the West, explored by 1st Lieut. Joseph C. Ives, Topl. Engrs. under the direction of the Office of Explorations and Surveys. A.A. Humphreys, Capt. Topl. Engrs. in Charge, by order of the Hon. John B. Floyd, Secretary of War. 1858. Drawn by Frhr. F.W.v. Egloffstein. Topographer to the Expedition. Topography by Frhr. F.W.v. Egloffstein. Ruling by Samuel Sartain. Lettering by F. Courtenay.
from davidrumsey.com, accessed June 12, 2015.

History

Fortification Rock, now an island, was before the building of

Boulder Dam #REDIRECT Hoover Dam Hoover Dam is a concrete arch-gravity dam in the Black Canyon of the Colorado River, on the border between the U.S. states of Nevada and Arizona. It was constructed between 1931 and 1936 during the Great Depression a ...

and the filling of Lake Mead, the tallest peak of a small range of hills, a landmark on the west bank of the

just above the top entrance to the

Black Canyon of the Colorado The Black Canyon of the Colorado is the canyon on the Colorado River where Hoover Dam was built. The canyon is located on the Colorado River at the state line between Nevada and Arizona. The western wall of the gorge is in the El Dorado Mountai ...

. It was named by 1st Lieutenant

Joseph Christmas Ives Joseph Christmas Ives (25 December 1829 – 12 November 1868) was an American soldier, botanist, and an explorer of the Colorado River in 1858. Biography Ives was born in New York City on Christmas Day, 1829. He graduated from Bowdoin Colleg ...

, March 11, 1858, during his 1857-1858 expedition to find the upper limit of navigation for the Colorado. It marked what he considered that highest point for

steamboat A steamboat is a boat that is marine propulsion, propelled primarily by marine steam engine, steam power, typically driving propellers or Paddle steamer, paddlewheels. Steamboats sometimes use the ship prefix, prefix designation SS, S.S. or S/S ...

navigation, during the June to October season of high water. He had left his

''Explorer'' behind at the mouth of the

after it had struck Explorer's Rock at its mouth. While it was being repaired, he and the steamboat's captain and mate had ascended the canyon in a

skiff A skiff is any of a variety of essentially unrelated styles of small boats. Traditionally, these are coastal craft or river craft used for leisure, as a utility craft, and for fishing, and have a one-person or small crew. Sailing skiffs have devel ...

portaging Portage or portaging (Canada: ; ) is the practice of carrying water craft or cargo over land, either around an obstacle in a river, or between two bodies of water. A path where items are regularly carried between bodies of water is also called a ...

over the rapids to camp two days later on the west riverbank at the foot of Fortification Rock, which had to him the appearance of a

fortification A fortification is a military construction or building designed for the defense of territories in warfare, and is also used to establish rule in a region during peacetime. The term is derived from Latin ''fortis'' ("strong") and ''facere'' ...

. Ives climbed it to get a look at the land and course of the river upstream. Joseph C. Ives, REPORT UPON THE COLORADO RIVER OF THE WEST, EXPLORED IN 1857 AND 1858 BY LIEUTENANT JOSEPH C. IVES, CORPS OF TOPOGRAPHICAL ENGINEERS, UNDER THE DIRECTION OP THE OFFICE OF EXPLORATIONS AND SURVEYS, A. A. HUMPHREYS, CAPTAIN TOPOGRAPHICAL ENGINEERS, IN CHARGE. BY ORDER OF THE SECRETARY OF WAR, GOVERNMENT PRINTING OFFICE, WASHINGTON, 1861; PART I. GENERAL REPORT.
/ref>

References

{{authority control Landforms of Clark County, Nevada Lake islands of Nevada Colorado River