Lets see one Google search on the word Dachau and lets start with this:
Concentration Camp Dachau : The Early Days
By the first of May, 1933, there were 1200 inmates in the camp; mostly political prisoners from Munich. These were comprised by "...members of the Social Democratic and Communist parties, many Catholics and many Jewish doctors and lawyers." 7 Guards began murdering inmates from the very first days of the camp's existence.
Close to the end of 1933, 4,821 registered prisoners had arrived in Dachau. By 1945, 206,206 prisoners had been registered. The total number of dead may never be known. Soviet prisoners of war were summarily executed by the thousands, civilians were assigned by the Gestapo to the camp for "Sonderbehandlung" ("Special Treatment," a Nazi euphemism which signified "killing"), and a great many died in evacuation marches and death marches. These deaths were never registered. The International Tracing Service in Arolson reports 31,591 dead among the prisoners that were registered.8
You can go to just this site if you wish
http://www.holocaust-history.org/dachau-gas-chambers/ or you can do a Google search and check any of the other 304,000 sites.