Of the rest of the land, 20.1% is settled (buildings or roads) and the remainder (0.6%) is non-productive (rivers or lakes).

It consists of the village of Gossau with the sections of Mettendorf, Niederdorf, Oberdorf and Watt and the village of Arnegg as well as the hamlets of Albertschwil, Enggetschwil, Geretschwil, Hochschoren, Hueb, Matten, Neuchlen, Rain, Rüeggetschwil, Rüti, Wilen, Zinggenhueb, Erlen, Herzenwil and Stöcklen.

In 1806 the hamlets of Arnegg (without Oberarnegg), Erlen, Fronackeren, Geretschwil, Herzenwil, Hölzli, Stöcklen, Wilen and Zinggenhueb came to Gossau from Andwil in exchange for Fronackeren, Hölzli, Landegg and Neuegg.

The blazon of the municipal coat of arms is Or a Cross bottony Gules issuant from jaws of a Wyvern passant Vert and in sinister chief a Bear rampant Sable langued and in his virility of the second.

Of the foreign population, (as of 2000[update]), 168 are from Germany, 487 are from Italy, 1,574 are from ex-Yugoslavia, 105 are from Austria, 214 are from Turkey, and 496 are from another country.

[8] The age distribution, as of 2000[update], in Gossau is; 2,007 children or 11.9% of the population are between 0 and 9 years old and 2,158 teenagers or 12.8% are between 10 and 19.

[4] Out of the total population in Gossau, as of 2000[update], the highest education level completed by 3,808 people (22.7% of the population) was Primary, while 6,416 (38.2%) have completed Secondary, 1,678 (10.0%) have attended a Tertiary school, and 670 (4.0%) are not in school.

[8] The historical population is given in the following table:[3] The Former Rubberband Factory at Stadtbühlstrasse 12 is listed as a Swiss heritage site of national significance.

It is a late gothic castle, with a high medieval south west wall and a modern chapel.

From the 2000 census[update], 9,608 or 57.2% are Roman Catholic, while 3,935 or 23.4% belonged to the Swiss Reformed Church.