The land area of Clark County is 8,061 square miles (20,880 km2), or roughly the size of New Jersey.

Native Americans lived in the Las Vegas Valley beginning over 10,000 years ago.

[5] Previously part of the Mexican Territory of Alta California, the Clark County lands were subsequently traversed by American beaver trappers.

Word of their journeys inspired the New Mexican merchant Antonio Armijo in 1829 to establish the first route for mule trains and herds of livestock from Nuevo Mexico to Alta California through the area, along the Virgin and Colorado Rivers.

What is now Clark County was acquired by the United States during the Mexican–American War, becoming part of the northwestern corner of New Mexico Territory.

The part of Pah-Ute County north and west of the Colorado River was assigned to the new State of Nevada in 1866; however, Arizona territory fought the division until 1871.

[6] Clark was largely responsible for construction of the San Pedro, Los Angeles and Salt Lake Railroad through the area, contributing to the region's early development.

Clark County is geographically coextensive with the Las Vegas MSA, a metropolitan statistical area designated by the Office of Management and Budget and used by the United States Census Bureau and other agencies for statistical purposes.

[7] Over time and influenced by climate change, droughts in Southern Nevada have been increasing in frequency and severity,[8] putting a further strain on Clark County's and Las Vegas's water security.

Greater Las Vegas is a tectonic valley, surrounded by four mountain ranges, with nearby Mount Charleston being the highest elevation at 11,918 ft (3,633 m), located to the northwest.

Many are separate entities that are managed by the Bureau of Land Management (BLM): Clark County has diverse desert flora and fauna, including higher-elevation mountain areas, the desert floor, and the Colorado River/Lake Mead ecosystems.

Correspondingly, air quality levels prior to the 1960s were in a favorable range, but the proliferation of automobiles with the human population expansion created circumstances where some federal air quality standards were violated starting in the 1980s.

[citation needed] To plan for the wave of development forecast by 1980, Clark County embarked on a regional environmental impact assessment funded by a federal Section 208 program, with Sedway Cooke conducting the planning work and Earth Metrics performing environmental analysis.

[citation needed] To prevent the loss of federal funds due to unacceptable dust levels in the Las Vegas valley, in 2003 the Nevada Air Quality Management division (under direction of Clark County officials) created the "Don't Be a Dusthole" campaign.

Nevada is the third most seismically active state in the U.S. (after Alaska and California); the United States Geological Survey has estimated that over the next 50 years, Clark County has a 10–20% chance of a (moment magnitude) M6.0 or greater earthquake occurring within 50 km (31 mi) of Las Vegas.

[26] The largest ancestries in the county were Mexican (23.2%), German (7.4%), Filipino (6.8%), English (6.8%), Irish (6.2%), and Italian (4.5%).

Other entities with police forces include University of Nevada, Las Vegas, the College of Southern Nevada, the Clark County School District, and cities of Henderson, Mesquite, Boulder City and North Las Vegas.

The Regional Justice Center replaced the Clark County Courthouse in 2005, and is about 3 blocks from downtown Fremont Street, at 200 Lewis Avenue.

The Las Vegas Justice Court Township the city of Las Vegas[43][44][45] and the unincorporated towns of Blue Diamond, Cactus Springs, Enterprise, Indian Springs, Mount Charleston, Paradise, Spring Valley, Summerlin South, Sunrise Manor (partially in North Las Vegas Township), Whitney (partially in Henderson Township) and Winchester.

[48][49] According to the Secretary of State's office, Independents comprise a plurality of registered voters in Clark County.

However, it is somewhat less Democratic than many other urban counties; the GOP candidate has received at least 39 percent of the vote in every election since 1996.

Both Kenny Guinn and Brian Sandoval carried the county in both gubernatorial terms they won, however.

In 2018, Dean Heller carried 15 of Nevada's 17 county-level jurisdictions in his bid for a second full term in the U. S. Senate.

In that year's gubernatorial election, Democrat Steve Sisolak lost 15 out of 17 county-level jurisdictions, but won Clark by enough of a margin to get the victory.

The city of Las Vegas itself leans Democratic, as do the communities of Paradise, Spring Valley and Enterprise.

The Regional Transportation Commission of Southern Nevada operates the RTC Transit system, and does planning for most major roadways.

Since 1999 the group has added more the 15,000 plants to stabilize the wash's banks and restore and expand the wetlands surrounding the wash. As part of the effort to restore the wash to a more natural state, they have removed more than 500,000 pounds (230,000 kg) of trash.

Las Vegas and Laughlin are still served by Amtrak Thruway service which connects to the Southwest Chief.