California State Route 99 (SR 99), commonly known as Highway 99 or, simply, as 99 (without any further designation), is a north–south state highway

State highway

State highway, state road or state route can refer to one of three related concepts, two of them related to a state or provincial government in a country that is divided into states or provinces :#A...

 in the U.S. state

U.S. state

A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...

 of California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

, stretching almost the entire length of the Central Valley. From its southern end at I-5 near Wheeler Ridge

Wheeler Ridge, California

Wheeler Ridge is an unincorporated community in Kern County, California. It is located south-southeast of Mettler, at an elevation of 955 feet .A post office operated at Wheeler Ridge from 1923 to 1972....

 to its northern end at State Route 36 near Red Bluff

Red Bluff, California

Red Bluff is a city in and the county seat of Tehama County, California, United States. The population was 14,076 at the 2010 census, up from 13,147 at the 2000 census....

, SR 99 goes through the densely-populated eastern parts of the valley.