Located smack-dab in the middle of the Arabian Peninsula, Riyadh is not only the Saudi capital but also the center of the Najd region, which alongside Hejaz (home to the port city of Jeddah and the holy cities of Mecca and Medina) forms the modern Saudi state. It was chosen as the capital because of its proximity to Diriyah, House of Saud's ancestral hometown, which neighbors Riyadh immediately to the west.
Originally known as Hajr, the city was founded by the tribe of Banu Hanifa. It was the capital of the province of Al-Yamamah, whose governors were responsible for most of central and eastern Arabia during the Umayyad and Abbasid eras. Al-Yamamah broke away from the Abbasid Empire in 866, and the area fell under the rule of the Ukhaydhirites, who moved the capital from Hajr to nearby Al-Kharj, with the city falling into decline and breaking up into several separate estates and settlements. The earliest known reference to the area by the name Riyadh comes from a 17th-century chronicler reporting on an event from the year 1590. In 1737, Deham ibn Dawwas, a refugee from neighboring Manfuha, took control of Riyadh. He built a single wall to encircle the various oasis towns in the area, making them effectively a single city. The name "Riyadh," meaning "gardens" refers to these earlier oasis towns.
In the 19th century, Riyadh was chosen as the capital of the Emirate of Nejd, the so-called "second Saudi state" established by the House of Saud. After a century of internecine struggles between the grandsons of founder Turki bin Abdullah bin Muhammad as well as conflict with the rivaling House of Rashid (centered on Ha'il, located 620 km northwest of Riyadh), Abdul Aziz Ibn Saud, whose father who had gone to Kuwait in exile after the collapse of the second Saudi state, returned to his homeland to declare the Sultanate of Nejd in 1921. In 1926, he defeated the House of Hashim, who had been ruling Hejaz since the 10th century. After a brief period of dual monarchy, Abdul Aziz united Najd and Hejaz into a single country called "Saudi Arabia" in 1932, with Riyadh as the capital.
From the 1940s onward, the city flourished from a relatively narrow, spatially isolated town into the modern, spacious metropolis it is now, with the development of Annasriyyah, the royal residential district, and the creation of entire neighborhoods and new settlements on grid plans, connected by high-capacity main roads to the inner areas.
