County in south central England, north of the Thames, and west and northwest of London; one of the Home Counties. The north is in the basin of the Ouse, the south in that of the Thames, the Chilterns lie between and made communications between the north and south of the county difficult before modern transport.
In the early days of Anglo-Saxon England, at least part of later Buckinghamshire was in the small kingdom or province of Cilternsaetna, while the Kingdom of the Gewisse, the forerunner of Wessex, may have held some of the southern lands. Later the whole area belonged to Mercia, and remained under English rule after the Danish conquest and settlement of eastern Mercia.
The shire was formed some time after English Mercia was absorbed in the Kingdom of Wessex by Edward the Elder in 918, and might have been formed while he still reigned. It took its name from Buckingham, which lies in the north of the county, the area nearest to the territory that had been under Danish rule and a place that had been fortified against the Danes. Buckingham has remained small in modern times and Aylesbury is the modern administrative centre.
The county belonged to the Mercian diocese of Dorchester, which became Lincoln in 1075. In 1837 it was transferred to Oxford.
Two members of the Giffard family were Earls of Buckingham, c.1100-1164. The Earldom was next created, in 1377, for Thomas of Woodstock, the youngest son of Edward III, also Duke of Gloucester from 1385. He died in prison and was forfeited in 1397. Humphrey, 5th Earl of Stafford, whose mother was Gloucester’s daughter, was created Duke of Buckingham in 1444. His great-grandson, the 3rd duke, was forfeited and executed in 1521. The families of Villiers, Sheffield and Grenville have all enjoyed the ducal title since; the last was extinguished with the death of the 3rd Duke in 1889.
The county is long from north to south, narrow east to west. There were no county boroughs, 1888-1974, even though Buckinghamshire was quite populous, increasingly so during the course of the 20th century. 33rd in area of the administrative counties, it was 16th in population (in 1971), and even among the geographical counties (that is, adding in the population of the county boroughs), it was 25th, but its population was spread, with no very large towns. The largest of them, Slough, with 87,000, fell below the limit for attempting to become a county borough.
Buckinghamshire was not greatly changed in area in 1972/4, but with the advance of Berkshire across the Thames it lost the considerable population of the Slough and Eton region. Even so, the expansion of its towns, including the New Town of Milton Keynes, more than compensated for the loss of Slough, and Buckinghamshire was 30th of all the English counties (including the metropolitan counties) before the reforms of the 1990s make comparisons more difficult. In 1997 Milton Keynes became a unitary authority, the modern equivalent of a county borough.