If you are looking for GIS data, the easiest place to find it may be the ArcGIS server. The url shows up in a google search for State Plane (NAD 83). I\’d expect the boundaries to be available from data.gov. But when I tried, none of the links worked.
To get the data directly from the server
From this page, copy the url and paste it into the ArcGIS Feature Server. Name it. Select it. Then add it to the map.
To open a lyr file on a Mac in QGIS
Download the file. Change the suffix from lyr to .zip.
Just unzipping may not work. So right click on the file and Open With Unarchive (instead of Archive Utility).
There will be a gdb that can be dragged directly onto your QGIS Project to use.
Thanks to this Stack Exchange thread.