Watch Duty, a service that tracks wildfires in 22 states, has become a critical resource forLos Angeles residents facing catastrophic wildfires.The app and website, run by a nonprofit thatcollects real-time dispatch information and vets alertsthrough a team of staff and about 200 volunteers, saw an increase of 600,000 users in a 24-hour period last week at the onset of the wildfires in Los Angeles County. In the week since the fires began, tens of thousands of structures have been destroyed and more than 100,000 people have been displaced, with at least 24 deaths.In addition to providing searchable maps and alerts of where wildfires are happening, Watch Duty provides air quality and wind direction information and resources on evacuation information and shelters, and it sends out alerts when fires threaten lives or properties. The service, which launched in 2021, has among its volunteers retired and active firefighters and dispatchers who help corroborate information from fire cameras, satellites, radio scanners, announcements from police and fire services, and user-submitted photos and tips.Watch Duty last week zoomed to the top of Apple's App Store download charts, as it has several times in the past during other wildfire incidents. It remains in the top 10 there this week, and likewise in the Google Play store.The nonprofit's CEO, John Clarke Mills, a software entrepreneur who started Watch Duty after a close call with a wildfire near his Northern California home, has said the success of the app has been "bittersweet." He wrote on LinkedIn this week, "Most days I absolutely love what I do, am truly honored to serve, and am so grateful for the privilege to do so. This is not one of those days.""The amount of destruction I have witnessed in less than 24 hours is really hard to take in. This is by far the worst I have seen since taking this job and it's not even close to over," Mills wrotelast week.As of Tuesday, a week after the blazes began, the sprawling Palisades fire is only 17% contained, and the Eaton fire 35%, according to The New York Times.The Los Angeles Timesreportedthat Watch Duty has raised $2 million in membership dues, $600,000 from donations and $3 million in grants. It grants additional features, such a tracker of firefighting aircraft, with memberships that start at $25 a year. As of mid-December, Watch Duty had more than 7.2 million active users.On social media, the app has been discussed and recommended by users includingESPN's Mina Kimes, Signal president Meredith Whittakerand CBS News correspondent Jonathan Viglotti.