Why is it der Walliser?

Walliser ends in -er, and most nouns ending in -er are masculine: in a German dictionary, 86% of them take der.

All nouns ending in -er
Sense 1
der

Meaning

[1] Residents of the Canton of Valais in the southwest of Switzerland

[1] Bewohner des Kantons Wallis im Südwesten der Schweiz

Examples

[1] "The Valais poet Maurice Chappaz and his first wife, the writer Sä Corinna Bille, have become a myth of Swiss literature."

[1] „Der Walliser Dichter Maurice Chappaz und seine erste Frau, die Schriftstellerin S. Corinna Bille, sind zu einem Mythos der Schweizer Literatur geworden.“

Declension

1 Singular Plural
Nominativ der Walliser die Walliser
Genitiv des Wallisers der Walliser
Dativ dem Walliser den Wallisern
Akkusativ den Walliser die Walliser

Pronunciation

Dictionary entries include material from Wiktionary. Wiktionary