Initially Zelwa was a private possession of various nobles, by the mid-16th century it became a possession of the
Polish Crown, and in the 17th century it became again a private possession of nobility, including the
Sapieha, Połubiński,
Radziwiłł, Jarmołowicz and Konarzewski families. In 1720 weekly markets and annual
fairs were established. Following the joint German-Soviet
invasion of Poland in September 1939, it was first
occupied by the Soviet Union until 1 July 1941, and then by
Nazi Germany until 12 July 1944 and administered as a part of
Bezirk Bialystok. When the Germans entered the town, they killed 40 to 50 Jewish men and kept the Jews of the town imprisoned in a
ghetto in very harsh conditions. In November 1942, the Jews were deported and murdered at the
Treblinka extermination camp. ==Notes==