The district capital is the town of Baden and the largest municipality is Wettingen, located in the Limmat Valley (German: Limmattal).

The district has a total of 25 municipalities, an area of 153.07 km2 (59.10 sq mi), and a population (as of 2014[update]) of about 138,000.

The first district of Baden existed during the existence of that canton, covering part of the former county, and upon its merging into the canton of Aargau, the contemporary district was formed.

Upon the merging of the canton of Baden into Aargau in 1803, the district gained the municipalities of Würenlingen, Bellikon, Künten, Remetschwil, Stetten, Mellingen, Wohlenschwil and Mägenwil (from neighbouring districts of the canton of Baden) but had to give up Hüttikon, Oetwil an der Limmat, Dietikon and Schlieren to the Canton of Zurich.

[4] From the 2000 census[update], 54,408 or 46.7% are Roman Catholic, while 32,482 or 27.9% belonged to the Swiss Reformed Church.