"Dahauua" = Lehmige Aue, means loamy plain
The oldest document about Dachau shows the date of 15th August 805. Therein is declared that Erchana, a Lady deriving from noble pedigree, had given her property - "at a place named Dachau"- to the cathedral of Freising.

About 1100, there was built a castle on top of the "Giglberg", a hill which was encircled by a tributary of the "Amper" flow. The counts did name themselves after the place of Dachau. After demolition of this castle in the year 1134 there was chosen a better site in the place of Dachau. In the year 1182, the last count of Dachau, Konrad III, died without having had children.

Thereupon, the Duke of Wittelsbach Otto I, acquired the castle of Dachau together with all the hereto belonging estates and ministerials, and created here in the "Office of Dachau" an administration centre. Therefore Dachau was the seat of a county court.

Round about 1240 Dachau was raised to a "market-place", about 120 years later this place received the right to keep a seal and was then a "free" market - place, becoming member of the "Landschaft", the provincial diet of the Bavarian estates of the realm.

In the year 1391 Dachau obtained the right for three fairs a year, each lasting four days. In that way, many people came to that place. Therefore the market was removed to the hill and supplied with three gates ("Tore") for reasons of security: Augsburger Tor, Freisinger Tor and Münchner Tor. For centuries Dachau remained the greatest market in Bavaria.

In the years 1558 to 1573 there was built on top of that hill, nowadays called "Schloßberg" (castle hill), a very imposing Renaissance castle with four wings. Now there is still resting the torso of one wing, which is very much admired today in the form Joseph Effner rebuilt this wing in the year 1715.

In the 19th century market wall and ditch were levelled, the construction of houses did expand outside of the old heart of the market. In the year 1868 the railway line Munich-Ingolstadt was completed. Only in the year 1933 the "market-place" was raised to a "town".