Martinez is a city and the county seat

County seat

A county seat is an administrative center, or seat of government, for a county or civil parish. The term is primarily used in the United States....

 of Contra Costa County, California

Contra Costa County, California

Contra Costa County is a primarily suburban county in the San Francisco Bay Area of the U.S. state of California. As of the 2010 census, it had a population of 1,049,025...

, United States. The population was 35,824 at the 2010 census. The downtown is notable for its large number of preserved old buildings. Martinez is located on the south side of the Carquinez Strait

Carquinez Strait

The Carquinez Strait is a narrow tidal strait in northern California. It is part of the tidal estuary of the Sacramento and the San Joaquin rivers as they drain into the San Francisco Bay...

 in the San Francisco Bay Area

San Francisco Bay Area

The San Francisco Bay Area, commonly known as the Bay Area, is a populated region that surrounds the San Francisco and San Pablo estuaries in Northern California. The region encompasses metropolitan areas of San Francisco, Oakland, and San Jose, along with smaller urban and rural areas...

, directly facing the city of Benicia

Benicia, California

Benicia is a waterside city in Solano County, California, United States. It was the first city in California to be founded by Anglo-Americans, and served as the state capital for nearly thirteen months from 1853 to 1854. The population was 26,997 at the 2010 census. The city is located in the San...

.
In 1824 the Alhambra Valley

Alhambra Creek

Alhambra Creek is a stream in Contra Costa County, California in Northern California which drains into the Carquinez Strait by way of the historical Arroyo del Hambre. Alhambra Creek and its valley take their name from Cañada del Hambre, Spanish for "valley of hunger", apparently because of some...

 was included in the Rancho El Pinole

Rancho El Pinole

Rancho El Pinole was a Mexican land grant in present day Contra Costa County, California given in 1842 by Governor Juan Alvarado to Ygnacio Martinez...

 Mexican land grant to Ygnacio Martínez. In 1847, Dr. Robert Semple

Robert B. Semple

Doctor Robert Baylor Semple was a 19th-century Californian newspaperman & politician.A newspaperman in Kentucky, he came west over the California Trail with Lansford Hastings in 1845, before the gold rush. During the 1846 Bear Flag Revolt, he led the Americans around Sutter's Fort in the...

 contracted to provide ferry service from Martinez to Benicia, which for many years was the only crossing on the Carquinez Strait.