Colusa County was one of California's original counties at the time of statehood, although portions of the county were later ceded to Tehama and Glenn counties. Today the county's economy is based primarily on agriculture, with rice and almonds accounting for approximately sixty percent of the total agricultural output.
- 1 Glenn County - Bordering Colusa County to the north, Glenn County is an agricultural region that is most likely to be experienced by travelers passing through on Interstate 5. While it lacks significant amenities, there are a few options for travelers to experience small-town America at events such as the Glenn County Fair, held in mid-May in the town of Orland, or at the Thunderhill Raceway Park outside of Willows, home to the longest automobile race in the United States: the 25 Hours of Thunderhill.
- 2 Butte County
- 3 Sutter County - Colusa County's eastern neighbor, tiny Sutter County lies between the Sacramento and Feather rivers, with nearly 90% of the county's land used for grazing and agriculture. The county is home to the eroded volcanic lava domes of the Sutter Buttes, which occupy a circular area roughly ten miles across and are sometimes referred to as the world's smallest mountain range.
- 4 Yolo County - With extensive farmlands, Colusa County's southern neighbor offers numerous opportunities for visitors to engage in agritourism: farmer's markets are held regularly, organic farms offer tours and the opportunity to pick your own produce, and more than 35 wineries can be found in the county. The college town of Davis is home to California's third-largest state university and boasts the highest number of bikes per capita in the USA, a statistic that led the US Bicycling Hall of Fame to move to the town in 2010.
- 5 Lake County - Rural Lake County lies west of Colusa County and is named after Clear Lake, a body of water that is believed to be 2.5 million years old and thus the oldest lake in North America. The lake is sometimes called the "Bass Capital of the West", and its 100 miles of shoreline offer ample opportunity for fishing, boating, swimming and birdwatching. The county is also home to the Clear Lake Volcanic Field, a region that includes lava domes, cinder cones, the 4,305 foot tall volcano Mount Konocti, and the world's largest geothermal field with more than twenty geothermal power plants.