San Diego is a city in the U.S. state of California on the coast of the Pacific Ocean, approximately 120 miles (190 km) south of Los Angeles and immediately adjacent to the border with Mexico. With an estimated population of 1,425,976 as of July 1, 2018, San Diego is the eighth-largest city in the United States and second-largest in California. It is part of the San Diego–Tijuana conurbation, the second-largest transborder agglomeration between the U.S. and a neighboring country after Detroit–Windsor, with a population of 4,922,723 people. The city is known for its mild year-round climate, natural deep-water harbor, extensive beaches, long association with the United States Navy, and recent emergence as a healthcare and biotechnology development center.

San Diego is renowned for its idyllic climate, 70 miles of pristine beaches and a dazzling array of world-class family attractions. Popular attractions include the world-famous San Diego Zoo and San Diego Zoo Safari Park, SeaWorld San Diego and LEGOLAND California. San Diego offers an expansive variety of things to see and do, appealing to guests of all ages from around the world.

• According to SDSU professor emeritus Monte Marshall, San Diego Bay is "the surface expression of a north-south-trending, nested graben". The Rose Canyon and Point Loma fault zones are part of the San Andreas Fault system. About 40 miles (64 km) east of the bay are the Laguna Mountains in the Peninsular Ranges, which are part of the backbone of the American continents. The city lies on approximately 200 deep canyons and hills separating its mesas, creating small pockets of natural open space scattered throughout the city and giving it a hilly geography.
• There were 17,700 people residing in San Diego in 1900, 147,995 in 1930, 573,224 in 1960, and 696,769 in 1970. By the mid-1970s, it displaced San Francisco as California's second-largest city. At the 2010 census, the population totaled 1,307,402, while that of the metropolitan area was 3,095,313.
  San Diego stands on land that rises gradually from the Pacific shore onto mesas or foothills of the Laguna mountain range. These are separated by numerous canyons that separate the 25 to 30 communities that make up the city. The climate is mild and semiarid, with an average temperature of 63° F (17° C) and an annual rainfall of about 10.4 inches (265 mm).
• A rapidly growing city, San Diego has been known in the past for its naval bases, its prominent role in early aviation development, and its proximity to Mexico. Since World War II, however, it has prospered upon a variegated commercial foundation that has included industry, agriculture, research, trade, tourism, and the city's great appeal as a place to live.
• Old Town, just west of the presidio, was the city's first civilian settlement and still contains restored early Spanish, Mexican, and American period homes. Part of Old Town is now a state park. The present Mission San Diego is 6 miles (10 km) to the east, in Mission Valley.
• Aquatic sports and ocean fishing are enjoyed most of the year, as is land recreation, with a multitude of parks, tennis courts, and golf courses in the vicinity. Mountains and deserts to the east attract campers, hikers, cyclists, and, in winter, skiers. Qualcomm Stadium is the home of the San Diego Chargers of the National Football League, and the San Diego Padres baseball team of major league baseball's National League calls Petco Park its home.
• Hypnotism is banned by public schools in San Diego.
• Charles Lindbergh made history when he flew from San Diego to New York and then non-stop to Paris on the Spirit of St. Louis in 1927. Built in 1863, the Star of India is the world’s oldest active-sailing ship which calls its home a port in San Diego. After completing 21 circumnavigations, the Star of India has survived being stuck in ice in Alaska and going aground in Hawaii
   

The city is governed by a mayor and a nine-member city council. In 2006, its government changed from a council–manager government to a strong mayor government, as decided by a citywide vote in 2004. The mayor is in effect the chief executive officer of the city, while the council is the legislative body. The City of San Diego is responsible for police, public safety, streets, water and sewer service, planning and zoning, and similar services within its borders. San Diego is a sanctuary city; however, San Diego County is a participant of the Secure Communities program. As of 2011, the city had one employee for every 137 residents, with a payroll greater than $733 million.

The largest sectors of San Diego's economy are defense/military, tourism, international trade, and research/manufacturing. In 2014, San Diego was designated by a Forbes columnist as the best city in the country to launch a small business or startup company.
 

Despite concerted efforts to encourage more housing construction, improve transportation and provide needed infrastructure, the future in those areas has become hazy.

Ambitious policies to boost housing density in hopes of creating more affordable homes may not be able to circumvent time-consuming environmental reviews following a California Supreme Court ruling.
Another delay in a long-awaited Mobility Action Plan for the city of San Diego has implications not only for attempts to reduce traffic congestion but for reaching goals to reduce greenhouse gas emissions from cars and trucks.
The city has increased spending on roads and other needed public works, yet an infrastructure funding shortfall continues to grow and now stands at $1.86 billion.
The recent developments may blunt emerging city plans on housing and transportation, but that doesn’t mean everyone’s upset about it. Critics have opposed more housing density in many neighborhoods, especially if proposals shortcut assessments of how it would impact residents and the environment. Meanwhile, motorists who don’t like government agencies pushing them toward alternative transportation are likely just fine with the mobility plan on the slow road.

For a long time, the city has been trying to catch up on fixing and building roads, parks, fire stations, libraries, drainage systems and more. It’s losing ground, according to Ashly McGlone of the Voice of San Diego. An analysis by McGlone revealed the city’s five-year shortfall in infrastructure financing is $286 million more than 2017. That’s after Faulconer substantially increased spending on repairing roads and after voters approved Proposition H to funnel more revenue to infrastructure projects started in 2018.