When I bring in the National Map or USA Topo map as a basemap in a web map in AGOL, they will not draw if I zoom in past 1:20000 or so (estimated). The plus button is disabled at these scales. Is there a scale limitation, and if so, how can I get around it? If I add these as basemaps in ArcMap they will zoom in as close as I need. Thank you.
There is a scale limitation.
"This reference map includes administrative boundaries, cities, protected areas, highways, roads, railways, water features, buildings and landmarks, overlaid on shaded relief and land cover imagery for added context. The map includes global coverage down to ~1:144k scale and more detailed coverage for North America down to ~1:9k scale."
The work around for AGOL is to use your own basemap.
You can load a basemap and add National Map as a layer. Then you should be able to zoom in as far as the basemap.