Archaeological evidence for the presence of people in Kildare in Neolithic times has been found. Those include the Broadleas stone circle, various standing stones, ritual sites, hill forts (including the royal site of Dún Ailinne), crannógs and toghers.

By 450 A.D. Christianity was established and churches were built. In the fifth century St. Brigid founded a monastery on the western edge of the Curragh Plain, near a stand of oak trees, on land donated by the King of Leinster. The settlement on the ancient Ridge of Clay (Druim Criaig) flourished and gave a new name, Cill Dara, ‘Church of the Oak,’ to the area.

Co. Kildare’s network of established monastic settlements were attacked continually by the Vikings. The town of Leixlip owed its origins to the Danish invaders and became the most westerly part of the Viking Kingdom of Dublin. Its name is derived from the old Norse for ‘Salmon Leap’ – ‘Lax-hlaup.’

In the 1170s the Anglo-Normans, took control of Kildare. Native Gaelic clans were deprived of their lands and sought refuge in the mountains of Wicklow and the bogs of Kildare, emerging only to launch sporadic attacks on the intruders.

In the sixteenth century the Tudors increased their power in Co. Kildare, while the Lord Protector, Oliver Cromwell, seized lands and initiated further plantations between 1649-53.

In May1798 the United Irishman Rebellion broke out in Co. Kildare. The family of the rising’s leader, Wolfe Tone, lived in Kildare and he is buried at Bodenstown, county Kildare.

Kildare was established as a county in 1297 and assumed its present borders in 1832.

In 1928 Co. Kildare became the first team to win the Sam Maguire trophy for the All-Ireland football championship, defeating Co. Cavan 2-6 to 2-5. Co. Kildare had won the All Ireland in 1905, 1919 and 1927.

The Fitzgerald  Norman dynasty controlled the House of Kildare from the 13/14th century and are identified in The Annals of the Four Masters as being "more Irish than the Irish themselves" .

It was at Ardscull in Kildare that Edward Bruce defeated Sir Edmund Butler in 1315.

In the 1630’s the power of the Fitzgerald’s was destroyed by King Henry V111 who arrested and killed the male line, apart from a boy, following the “Silken Thomas rebellion”. This boy would regain some of the family titles after the death of Henry.

Another famous Kildare man and military leader of the 1798 rebellion was Lord Edward Fitzgerald, the son of the Duke of Leinster. He was mortally wounded while resisting arrest in June 1798.

The Fitzgerald's held extensive estates and had many castles in the county, the principal one being at Maynooth.

The Irish Parliament meets at Leinster House which was once the palace built for the Earl of Kildare one of the Fitzgerald Dukes of Leinster.