Elis, or Eleia, an ancient district of southern Greece, bounded on the north by Achaea, east by Arcadia, south by Messenia, and west by the Ionian Sea. The local form of the name was Valis, or Valeia, and its meaning, in all probability, “the lowland.” In its physical constitution Elis is practically one with Achaea and Arcadia; its mountains are mere offshoots of the Arcadian highlands, and its principal rivers are fed by Arcadian springs.
Elis was divided into three districts - Hollow or Lowland Elis, Pisatis, or the territory of Pisa, and Triphylia, or the country of the three tribes. Hollow Elis, the largest and most northern of the three, was watered by the Peneus and its tributary the Ladon. The district was famous in antiquity for its cattle and horses. Pisatis extended south from Hollow Elis to the right bank of the Alpheus, and was divided into eight departments called after as many towns. Triphylia stretches south from the Alpheus to the Neda.
Modern history of Elis, now Elia, and more can be found here.
Edited and wikified from an encyclopedia of 1911