I am looking to share official GIS data with Apple Maps for our county. Does anyone know where or how to do this? I am the 911 director for the county. Thanks.
Although incorporating GIS data and features specific to a county, or specifically for responders to use may not be the best fit for a consumer app like Maps, you may want to look into creating your own specific app using MapKit.
The MapKit framework (https://developer.apple.com/documentation/mapkit/) allows you to use the generic Apple Maps, and also would allow you to layer specific map tiles on top of the default views, displaying the GIS data based views that way.
But all this depends on what kind of GIS data you are trying to display.