Muir Beach, CA has a population of 248 and is the 23,464th largest city in the United States. The population density is 503 per sq mi which is 117% higher than the California average and 455% higher than the national average. The median age in Muir Beach is 62 which is approximately 72% higher than the California average of 36. In Muir Beach, 60% of the population over 15 years of age are married, 95% speak English and 0% speak Spanish. 36% of Muir Beach residents were born in California, 54% were born out of state, 0% were born outside of the United States and 10% were foreign born.