Okara became Teshil Headquarters in 1918 when a network of canal irrigation was completed in the area. Okara district started functioning as district with effect from July 1, 1982.Its area is about 4,377 square Kilometers. It is situated at a distance of about 120 Kilometers from Lahore on Lahore-Multan Grand Trunk road.
Depalpur has a great historic past and is a very ancient town. The fortified town of Depalpur is built on an old Kashan site (40 A.D. to 172 A.D.). The fortifications themselves are very ancient; though it is impossible determine their dates. All that can be said is that they are older than the visitation of Taimur (1398 A.D). According to Ibnash Chandra Das, about 2,000 years ago, Depalpur was a habitat of Aryans( his book is Rig-Vedic India). He is a Bengali historian. From the time of Alexander to the time of Mehmood Ghaznavi, no account of Depalpur is, however, available. In older times, Depalpur fell on the way to Delhi and, as such, was considered to be a place where an invader could be engaged. Depalpur, therefore, was one of the 3 lines of defense; the other 2 begin Uch Sharif/Multan and Samana/Sunam and Hansi.Aaeen-e-Akbari(Vol 1 Part п,page 1042, by Abul Fazal,translated by Maulni Muhammad Fida) reveals that Militia Force at Depalpur, during of Abul Fazal, consisted of 5,210 mounted Horsemen and 53,300 infantry. Depalpur Sarkar (an Administrative Unit under Mughal Rule) had 29 Mahals, (the word in all probability) is ?Mahal? meaning a Revenue Estate, comprising an area of 1,433,767 Bighas and 8 Biswa yielding and annual income of 1,293,153 Dirham.
The Mongols invaded this part of the Country repeatedly and they were checked at Depalpur by Ghias-Ud-Din Balban and his son Shahzada Muhammad. During there last invasion of Punjab in 1285 A.D. Pir Muhammad Khan Mangol (also called Samar Khan) was defeated at Depalpur but during the pursuit of the retreating Mongols, Shahzada Muhammad was killed .It is believed that Shahzada Muhammad is lying in rest in a small tomb to the west of the Badshahi Mosque at Depalpur. Conformation from any authentic sources is, however, not available.
According to the Gazetteer of 1935,the town was founded by one Siri Chand it was called Siri Nagar after time, The present name of the town is said to have re-founded the town, one view is that the town was named after Raja Deva Pala. In the 14th Century, Feroze Shah Tughlaq regularly visited this place. It is also believed that he built a large Mosque outside the City, no longer to be located now. At the time of Taimur’s invasion, Depalpur was second to Multan in size and importance. The town, it is believed may have been deserted due to Taimurs’s invasion and drying up old Bias River.