Map of Euskal Herria with municipalities in historical Gascony.
A/B Municipalities of Gipuzkoa in historical Gascony
B Pasaia/Los Passatges (where Gascon was spoken until the XXth century; star: Sent Sebastian/Donosti and Hont Arràbia/Hondarribia where Gascon had been spokrn)
C/D Municipalities of Lapurdi in historical Gascony
D Gascon-speaking municipalities of Lapurdi (star: St Joan de Lus/Donibane Lohitzune where Gascon had been spoken)
E Municipalities of Nafarroa in historical Gascony
F/G Municipalities of Lower Navarra in historical Gascony
G Gascon-speaking municipalities of Lower Navarra
H/I Municipalities of Zuberoa in historical Gascony
I Gascon-speaking municipalities of Zuberoa
J Basque-speaking municipalities in Bearn
L Basque-speaking municipality in Lower Adour
M Lower Adour (linguistic and historical Gascony).

Data taken from the map of Gascony by Halip Lartiga (gasconha.com), see also Ronjat and OC.WP article about Los Passatges.
Own work
Jfblanc