@HighIQ -

1) Unfortunately, the go-to high-level lexile list is not as great as I thought...
https://hub.lexile.com/find-a-book/search
Enter range 1500 to 1825 (the max it will allow).
When you get the results list, slide the selection criteria higher: 1850 - 2200. Click "Apply Filters"
See 167 results.
The Emancipation Proclamation has the highest lexile level in this database: 2040.


2) This archived Lexile Map shows 1700 as the highest entry in its database: (copy/paste entire link)
https://web.archive.org/web/20130228070655/http://www.lexile.com:80/m/uploads/maps/Lexile-Map.pdf