Lying between the natural boundaries of the Wicklow mountains in the east and the River Barrow to the west, Kildare is a relatively prosperous county (one of its villages is actually named "Prosperous"), with large cattle and sheep farms, and a strong tradition of stud farming linked to the famous race-course at the Curragh.
Before the arrival of the Normans, the region was part of the territories of the O'Byrnes and O'Tooles. Following the granting of the county to the Norman Fitzgeralds, these were forced to migrate east, into the barren and impregnable Wicklow mountains. The Fitzgeralds became earls of Kildare and, later, Dukes of Leinster, and were virtual rulers of Ireland up to the sixteenth century. The seat of the Irish Oireachtais (parliament), Leinster House in Kildare Street, Dublin is named for these Fitzgeralds.
In recent years, the county has seen a large growth in its population, due almost entirely to the expansion of the suburbs of Dublin.