My top 5 in no particular order:
Magnepan - My favorite was the Tympani IV but required very carefully setup. Haven't heard the 20s yet.
Rockport - Much more musical speakers than Magico or YG Acoustics.
Ridge Street Audio Design Sason - Best 2-way I've ever heard including the Magico Minis.
Martin Logan - Only there full range design CLS, haven't heard the CLX yet. All their hybrids have a bothersome discontinuity I can't get past.
Wisdom Audio - Heard the Adrenaline around $40-50k at the time. One of the few speakers made of US made driver (BG planar magetic push pull "ribbon" driver) besides Magnepan. But too expensive and too complex.
Defunct Apogee - Now copied in technogy and looks by several companies. One of the most transparent sound equal to electrostats but with more body and subastance. Could approach the dynamic bass
impact of cone speakers better than Magnepan or any electrostatic
designs I've heard.
Acoustat - Another defunct company but it was the first electrostatic I've ever heard. Amazingly transparent. I heard the models with the direct drive OTL tube amps build in are quite remarkable. Heard the defunct Beveridge but it was all midrange with no real extension.
Unfortunately some of the most innovative US speaker makers have long disappeared.