Why is it der Stockholmer?

Stockholmer 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] person who comes from Stockholm or lives there

[1] Person, die aus Stockholm stammt oder dort lebt

Examples

[1] The Stockholmer have a very modern transport system

[1] Die Stockholmer verfügen über ein sehr modernes Verkehrssystem.

Declension

1 Singular Plural
Nominativ der Stockholmer die Stockholmer
Genitiv des Stockholmers der Stockholmer
Dativ dem Stockholmer den Stockholmern
Akkusativ den Stockholmer die Stockholmer

Pronunciation

Dictionary entries include material from Wiktionary. Wiktionary