San Diego is a city located in the southern part of California, USA, adjacent to the Pacific coast and the Mexican border. With a population of about 1.43 million, it is the second largest city in California after Los Angeles and the eighth largest in the United States. The San Diego area has developed from the Native American era through Spanish, Mexican, and American rule to the present day.

Native American Era
The San Diego area has been inhabited by Native Americans for about 12,000 years. The Kumeyaay tribe is a representative group that utilized abundant natural resources for agriculture, fishing, and hunting. The Kumeyaay settled around the San Diego River, forming a unique culture and social structure.

Spanish Colonial Period
In 1542, Spanish explorer Juan Rodríguez Cabrillo discovered San Diego Bay, marking the beginning of contact with Europeans. In 1769, an expedition led by Gaspar de Portolá established the first Spanish mission in the area, Mission San Diego de Alcalá. This was the first European settlement in California, which later began to develop around agriculture and livestock.

Mexican Rule and American Annexation
In 1821, Mexico gained independence from Spain, and San Diego became part of Mexican territory. During this period, the Rancho system was introduced, leading to the formation of large farms, and San Diego grew as a center for livestock and agriculture. However, after the Mexican-American War in 1848, San Diego was incorporated into the United States under the Treaty of Guadalupe Hidalgo.

American Annexation and Urban Development
After the annexation, San Diego began to develop as an important port city in California. By the late 19th century, the opening of the railroad led to a rapid population increase, establishing it as an economic center. In the early 20th century, military facilities and naval bases were established, making it a hub for the military industry, which became a significant part of the city's economy.

San Diego boasts a mild Mediterranean climate year-round, with average temperatures of 75°F (24°C) in summer and 65°F (18°C) in winter. The average annual rainfall is about 9.9 inches (251 mm), with many clear days suitable for outdoor activities.

Economy and Industry
San Diego has developed various industries, including military and defense, tourism, international trade, biotechnology, and medical research. The presence of a naval base plays a crucial role in the military industry.

Education and Culture
San Diego is home to major universities such as San Diego State University (SDSU) and the University of California, San Diego (UCSD), known as centers for education and research. Additionally, attractions like the San Diego Zoo, Balboa Park, and Seaport Village offer visitors rich experiences.

Transportation
San Diego International Airport (SAN) connects the city domestically and internationally, with well-developed highways and rail networks for convenient transportation. Public transport includes the San Diego Trolley and bus system. The downtown area is relatively small for a city of its size, and public transport connects residential areas with the city center efficiently. The trolley consists of three lines: Orange, Green, and Blue, all starting from residential areas and passing through downtown to near the Mexican border, making it a very convenient mode of transport. The bus system also covers suburban areas and allows transfers to the trolley. A monthly pass for unlimited use of the trolley and buses is $72 (as of 2024), a single bus fare is $2.25, and the trolley fare is $2.50.

Attractions
San Diego is famous for its beautiful beaches and various attractions. Notable places include La Jolla Cove, Coronado Island, Gaslamp Quarter, and Old Town San Diego, with family-friendly destinations like SeaWorld San Diego and LEGOLAND California also being popular. Balboa Park, the San Diego Zoo, and the Gaslamp Quarter area are attractions where modern city life harmonizes with historical traces.