The Kharj region is defined largely by the wide valley known as Wadi al-Sahba (sometimes known as "Wadi al-Kharj"), where the floods of many other wadis, such as Wadi Hanifa, are deposited. In addition, there were historically several fresh water springs (called asyah or uyun) that flowed towards the surface through apertures in the earth. As a result, the Kharj district has historically been one of the richest locations in Arabia in water resources, and has supported grain production since ancient times. However, springs of al-Kharj, like those of neighboring al-Aflaj have completely dried up in the last two decades. In previous time periods, the district was more often known as Jaww, Jaww al-Yamamah, or Al-Khadharim, though the name "Al-Kharj" was also known. The pre-Islamic legend of the tribes of Tasm and Jadis, is set in the Kharj district. At the beginning of Islam, al-Kharj was inhabited by the Bakr tribes, especially the Banu Hanifa. In 862, the Alid clan of the Ukhaydhirites fled to al-Kharj from the Hejaz, and made its main city, Al-Khidhrima, the capital of a small state. In the 18th century, the Kharj district was, along with the town of Riyadh, the most stubborn foe of the First Saudi State, and was among the very last areas of Najd to fall under Saudi rule. However, the district later became among the most loyal regions to the Al Saud, providing refuge to Turki ibn Abdallah from the Egyptian occupation in the 1820s, and joining Ibn Saud's campaigns in the early 20th century at an early date