California.
Start with the right source.

Find the source for your part of California.

The inventory is a way to begin a local information search, not a substitute for the agency responsible for an address. Start with your city or county’s official website, identify its police service provider, and check its current warning subscriptions and reporting instructions. A municipal name does not always identify a separate police department.

Among the larger places in this inventory are Los Angeles, San Diego, San Jose, San Francisco, Fresno. These names and estimates come from the Census source linked below. Population describes a place; it does not establish the number of app users, participating departments or people receiving alerts.

Choose the channel for the task.

State emergency management resources are a useful starting point for preparedness and official information. A local police agency’s reporting page answers a different question: which incidents it accepts, which recipient is appropriate and whether a self-service route fits the circumstances. Check those eligibility instructions before sending personal information or evidence.

If you need information for several places, keep their sources distinguishable. Home, work and family may connect you to different authorities. Following a participating agency in Lucas is separate from subscribing to official warnings, and a directory entry does not confirm that a department publishes in Lucas or accepts Lucas tips.

Read the inventory with its limits in view.

The table uses a population threshold to keep a national research inventory manageable. It is not a complete list of neighborhoods, unincorporated communities or all census-designated places. A missing place may still have official services and warnings. Use the relevant city, county or state source to continue the search rather than treating absence here as evidence that a service is unavailable.

For a researched local page, follow the original official links and look for the latest instruction. For a department considering Sentinel, begin with a discussion of the actual workflow and operating responsibilities. Information-finding, product evaluation and emergency assistance are distinct tasks; this directory is for the first of those.