Mahfooj - I know how to add a MAP LAYER. Thanks for the screenshot.
My question is, I want to display a US COUNTY LAYER to begin with. When I zoom in, I want to remove the county layer and show the underlying POINTS. The idea is, to avoid having to load all the 146 Million lat,lon at once but rather only for the city that i am zoomed into.
SInce you're hoping to change mark types, maybe you want to try building two visualizations with navigation between them. This way you can allow someone to drill down to the county level on your polygon view, then once a county is selected it takes them to the second view with the individual points plotted out. You can build the navigation using a selected action so that it won't seem like the user is actually switching between dashboards. This article shows how to build that action about halfway down, if you're not already familiar.
Hope this helps!