San Diego County's Board of Supervisors District 3 is a coastal and urban district that begins in the south with the City of Coronado and stretches northward along the coast, encompassing a series of coastal cities and communities within the City of San Diego.

The district includes the entirety of Coronado, known for its historic charm, naval base, and picturesque beaches. As it extends northward, the district takes in the coastal areas of the City of San Diego, capturing the essence of Southern California's beach culture with communities like Ocean Beach, Pacific Beach, and Mission Beach, each known for their unique blend of recreation, local businesses, and vibrant community life.

Further up the coast, the district covers the entire cities of Del Mar, Solana Beach, Encinitas, and Carlsbad. Del Mar is renowned for its racetrack and beaches, while Solana Beach is appreciated for its artsy atmosphere and small-town feel. Encinitas, with its surfing heritage and botanical gardens, and Carlsbad, known as 'The Village by the Sea,' add to the district's coastal allure and thriving local economies.

Within the City of San Diego, District 3 encompasses coastal and near-coastal communities such as La Jolla, with its mix of upscale living, academic institutions, and natural beauty. Moving inland, the district includes Carmel Valley, a suburban community known for its family-friendly atmosphere and quality of life.

The district's northern boundary extends to, but does not include, the cities of Oceanside, Vista, San Marcos, and Escondido. Instead, it includes areas such as Rancho Santa Fe, known for its rural charm and luxury estates, and parts of the San Dieguito area, adding a mix of suburban and semi-rural elements to the district.

The inclusion of communities like Mira Mesa, Rancho Peñasquitos, and Scripps Ranch in the district brings a suburban quality, with their residential neighborhoods and business hubs. The district also reaches into parts of the University Community, encompassing areas influenced by the University of California, San Diego.

Overall, District 3 presents a diverse array of communities, from affluent coastal towns and beachside neighborhoods to suburban enclaves and areas with rural characteristics. This diversity encapsulates the varied lifestyles and environments found along San Diego County's coastline, making District 3 a unique and dynamic part of the region.