There are approximately 15,572 SEO agencies in the United States as of 2025. The biggest marketing states are also the ones where you’ll find the most SEO companies.
The undisputed winner when it comes to the number of SEO companies is California. San Francisco (966) comes in first, Los Angeles (853) second, and San Diego County (996), third.
When combining San Diego County with other small cities including La Mesa, Chula Vista and La Jolla, San Diego becomes the biggest city where you’ll find the most SEO companies around.
It’s not surprising that San Diego of all cities is the place where you’ll find the most SEO agencies and SEO experts. Even though San Diego County only has a population of 3.3 million compared to Los Angeles (18.7 million) and San Francisco (8.8 million), San Diego, CA is considered the city with best climate in the US. If you are an SEO expert and a good one at that, San Diego is the city to live. Although it’s also considered the most expensive city compared to San Francisco and New York, it seems that successful SEO agencies tend to be headquartered in San Diego.
