The map provided plots the locations of Polish Roman Catholic Churches in the Archdiocese of Chicago. These are the churches identified in Joseph John Parot's book, Polish Catholics in Chicago: 1890-1920.
When you hover over a church icon, it will display the name of the church so you can determine if it's the church you are looking for. Since many churches are clustered together, zooming-in on a neighborhood will spread the church icons further apart to make it easier to select your church of interest. Also, if you are zoomed out too much, the icons do not line up with the locations as accurately. Keep in mind that some churches have closed although the buildings are usually still at their original locations. The map is based on addresses that often refer to the rectory since the churches themselves don't have mail delivery boxes. Clicking on a church icon will bring up the address. When you zoom into a location and turn on the Satellite view, you can usually find the church building fairly easily. You can also take a "walking tour" of the area from the map.
The Archdiocese of Chicago consists of Cook and Lake Counties in Illinois. These are highlighted with a reddisch background color. The church icons are in various colors. A red church icon indicates that this site has indexed both the marriage and baptismal records of that parish and the indexes are available to subscribers. A green church icon indicates that this church was founded after 1915, so its records are not generally available to the public.