Allendale, CA has a population of 1,349 and is the 13,323rd largest city in the United States. The population density is 220 per sq mi which is 5% lower than the California average and 143% higher than the national average. The median age in Allendale is 54 which is approximately 51% higher than the California average of 36. In Allendale, 62% of the population over 15 years of age are married, 93% speak English and 3% speak Spanish. 57% of Allendale residents were born in California, 38% were born out of state, 1% were born outside of the United States and 5% were foreign born.