Until the Third Partition of Poland the Miedzyrzec estate constituted the greatest private property of the Mielnik area. For a long time, from the 16th to the mid 17th century, the question of the estate's administrative status remained unresolved. Until the mid 17th century there was a dispute over the jurisdiction of this property between the gentry of Mielnik and Brzesc territories. Eventually it became a part of Mielnik area of the Province of Podlasie. One of the sources describing the essence of the dispute is the printed document of 1622, entitled 'Commisia albo proces Graniczenia miedzy woiewodztwem Podlaskiem, a miedzy woiewodztwem Brzesckiem WXL dla wiadomosci, że te granice iuste & legitime stanely”. This print contains several earlier documents, the oldest of which is the charter of 1 July 1390, endowing the knight, Abraham Chamiec, with the estates of Miedzyrzec and Stolpno on the River Krzna, then belonging to the Drohiczyn area. The endowed, Abraham Chamiec, was a knight of the Little Poland house of Gryf. His father was Cracow's Master of the Royal Hunt, Marek Chamiec of Rudno. Abraham had one brother, Jan. Apart from Miedzyrzec, Abraham Chamiec owned also estates in Cracow and Lublin territories. In 1409, he was also mentioned as castellan of Gostyn. Abraham Chamiec had five daughters and no male offspring. His daughters contributed their shares of property to other families. The only thing that remains unclear is how the Miedzyrzec estate, which already in 1428 belonged to the knight, Mikołaj Nasuta, stopped being a part of Abraham's or his family's property. Bestowment of Miedzyrzec upon Abraham Chamiec in 1390, although short lasting, is nevertheless important, mainly due to the fact that it is the oldest bestowment of the landed property in the Podlasie region.