The area covered by modern Warsaw had been inhabited for at least 1400 years. Several archaeological findings date back to the times of the Lusatian culture.
The first fortified settlements on the site of today's Warsaw were Bródno (9th/10th century), Kamion (11th century) and Jazdów (12th/13th century). Bródno was a small settlement in the north-eastern part of today's Warsaw, buried about 1040 during the uprising of Miec?aw – one of the Mazovian local princes. Kamion was established about 1065 close to the today's Warszawa Wschodnia station (today – Kamionek estate), Jazdów – before 1250 by the today's Sejm. Jazdów was raided twice – in 1262 by Lithuanians, in 1281 by the P?ock prince Boles?aw II of Masovia. Then, a new similar settlement was established on the site of a small fishing village called Warszowa, ca. 3.5 kilometres (2.2 mi) north of Jazdów – by the same prince Boles?aw II. The Boles?aw's brother and successor, Konrad II, built a wooden castellan, which was buried – again by the Lithuanians. On this place, the prince ordered to built a brick church, which obtained the name of St. John and became a cathedral.
The first historical document attesting to the existence of a Warsaw castellan dates to 1313. Fuller information about the age of the city is contained in the court case against the Teutonic Knights which took place in Warsaw cathedral in 1339. In the beginning of the 14th century it became one of the seats of the Dukes of Masovia, becoming the capital of Masovia in 1413 (prince Janusz II). Fourteenth-century Warsaw's economy rested on crafts and trade. The townsmen, of uniform nationality at the time, were marked by a great disparity in their financial status. At the top were the rich patricians while the plebeians formed the lower strata.
In that time, in Warsaw lived about 4500 people. During the 15th century, the town became to spread – beyond the northern town wall a settlement came into existence, which was called New Town, whereas the already existing settlement was called Old Town. Those two towns had their own town charters and own governments. The aim of establishing a new town was to regulate the settling of new people who weren't allowed to settle in Old Town (mainly Jews)
In 1515, during Muscovy-Lithuanian War fire incented probably by Russian agents burned great part of Old Warsaw. The differentiation and the growing social contrasts resulted in 1525 in the first revolt of the poor of Warsaw against the rich and the authority they exercised. As a result of this struggle the so-called third order was admitted to the city's authorities and shared power with the bodies formed by the patricians: the council and the assessors. The story of Warsaw populace's struggle for social liberation dates from that first demonstration in 1525.
Upon the extinction of the local ducal line, the duchy was reincorporated into the Polish Crown in 1526 (according to the gossips, the last Mazovian prince Janusz III was poisoned on the orders of Polish Queen, Bona Sforza, King Sigismund I).