You must be trying to book state or federal sites. What we've found is that private parks in the area usually have sites up until almost the day of. Especially midweek. Often for essentially the same money, you can get FHU's. Also, depending on the area, public parks slightly inland will often have sites. California has failed to use our tax dollars to provide a commensurate increase in camping facilities related to the increase in populace. We have only used a public facility once in the last decade. And using the required online booking was primitive compared to what private facilities usually provide.