Until 1946, Ketrzyn was called Rastenburg. The name was presumably derived from the prussian word "Rast" (post). The city is situated next to the Guber river which is an inflow of the Alle river. Originally, a settlement of the prussian Barten was located at that place. In 1329, the German Teutonic Knights built a wooden fort next to it. The fort with a surrounding of earth work and palisades was used as a border guard. It's task was to protect the area against Lithuanian attacks. However, the fort and the surrounding settlement was captured and destroyed by the Lithuanians in 1345 and 1348. Due to its geographic location, the fort was rebuilt immediately. In 1350, the Teutonic Order started building a massive defensive wall. When all reinforcements had been completed in 1357 and the castle had been enlarged, the settlement received town charters.

Church in Ketrzyn

The construction of the defensive installations with 13 bastions was finished in the late 70's of the 14th century. The south-western corner of the city wall was a church with a bastion and two cylindrical turrets. Two gates and one portal which could be reached on the waterway led into the city. In 1440, Rastenburg joined the Prussian Union. After the thirteen-years-continuing-war the city still belonged to the area of the Union. Later it belonged to the dukedom of Prussia.

The Grenadier Regiment which was founded in 1626 and was the oldest prussian regiment in garrison, was stationed in Rastenburg. Later it named itself "King Friedrich der Große". Colonel Hillebrandt von Kracht who was the founder of the regiment of 1626 had following slogan: "Live consistently, no bad luck is everlasting!". Until the middle of the 17th century, Rastenburg was known as the third wealthiest city in (Eastern-)Prussia behind Königsberg and Memel. Due to natural catastrophes, fires, looting during the wars after the time of the Union and also the plague, the wealth vanished rapidly. Still, the city was lucky that the defensive installations resisted the attack of the Tataren in 1656 and that the inhabitants were spared of the Big Plague form 1709 to 1711.

The Town Council of Ketrzyn

Since the beginning of the 18th century, the administrative district Rastenburg existed and combined the head offices Bartenstein, Rastenburg, Barten and Gerdauen. This division of the administrative district came from the administrative reform in 1818 and lasted until 1945. During World War I, Rastenburg was occupied by the Russians for almost two weeks. The city suffered little damage. Only the officers´ mess burned down.

World War II brought considerable destruction which mainly occured after the occupation. Here is to mention that near Rastenburg Hitler had his head quarters, the so called "Wolfsschanze". At this place the attempt of the terrorist attack of the group around Earl of Stauffenberg took place in 1944.

After the war the Polish people named the city after a notable mazurian historian: Wojciech Ketrzynski. He worked many years as scientist at the Ossolinski-Institut in Lemberg. He was committed as a propagandist for the Polish mazury (national traditions).

Today the city has a population of 35 thousands.