This is the 527th most frequent Swedish word.
stockholms
"Stockholms" is the genitive form of "Stockholm," meaning "Stockholm's" (possessive form, referring to something belonging to Stockholm).
In this sentence, 'Stockholms' is a possessive form, indicating the city of Stockholm's possession of the entity referred to (stad).
Stockholms stad är känd för sin skärgård.
The city of Stockholm is known for its archipelago.
Here, 'Stockholms' is used as a possessive noun, describing something related to the city of Stockholm (tunnelbana).
Jag köpte en karta över Stockholms tunnelbana.
I bought a map of Stockholm's subway.
In this case, 'Stockholms' indicates 'relating to Stockholm,' describing the nature of the history (associated with Stockholm).