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The term "Lanao" is derived from a Maranao word "Ranao" meaning a body of water. "Meranau" means lake dweller. They are the natives of the place occupying the land around Lake Lanao, which is situated at the central part of Lanao del Sur. Lanao, applies to the entire area before its division. When it was divided into two provinces, the southern portion became Lanao del Sur and the northern part became Lanao del Norte.
Dansalan, Marawi City's old name, was explored by the Spaniards as early as 1639. It is said that at that time, Marawi was already the citadel of Malayan-Arabic culture in Mindanao. Feeling the pulse of strong refusal among its inhabitants to adopt Christianity, the Spaniards abandoned the project of colonizing the area. Dansalan, physically speaking, would have satisfactorily qualified to become a town or municipality during the time of said exploration based on the Spanish Policy of "Ecclesiastical Administration" except for fanatical resistance of the natives who were mostly under Muslim rule.
A strong Spanish expedition to conquer the Maranaos was fielded in 1891 during the time of Governor General Valeriano Weyler, but this force was driven back to Iligan after failing to capture Dansalan. In 1895, Governor General Blanco sent a stronger force to take Marawi that thanks to superior firepower finally overrun the last defenses. The Spanish forces won a decisive victory and were able to erect a garrison in Dansalan and they already took with them Chabacanos and Chabacano-speaking Muslims from Zamboanga and Basilan and Cebuanos. However, they had to abandon it just four years later after the outbreak of the Spanish–American War in 1898, leaving it on the hands of the new American colonizers, who imposed their own rule on the population.
On May 24, 1904, the American Colonial Government proclaimed Dansalan a regular Municipality. The Philippines was still under the Commonwealth regime of the Americans when Dansalan was chartered into a city in 1904. In 1914, the Department of Mindanao and Sulu was created and Lanao was converted as a province.
The passage of Republic Act No. 2228 divided Lanao into two (2) provinces giving birth to Lanao del Norte and Lanao del Sur. The new province was inaugurated on July 4, 1959 making Iligan City as the capital of the north and Marawi City for the south. During the establishment process of the Autonomous Region of Muslim Mindanao, Lanao del Sur (and later Marawi City) voted to be part of the new autonomous region, while Lanao del Norte chose to remain in Northern Mindanao.
- 1914-09-01: Department of Mindanao and Sulu provided with autonomous government through Act No. 2408 enacted on July 23, 1914. Bukidnon sub-province and the former Moro Province districts of Cotabato, Davao, Lanao, Sulu and Zamboanga converted to provinces.
- 1941: Followed in World War II, Japanese fighters and bomber planes invaded and destroyed the areas around Lanao.
- 1942: Japanese Imperial forces occupied the province of Lanao.
- 1942: Local Christian and Muslim troops of the 101st Infantry Division, Philippine Commonwealth Army, USAFFE defended the fall the province of Lanao and attacking Japanese. After the Fall of Lanao on 1942, troopers of the USAFFE 101st Division was surrender by the Japanese forces and they captured in the province before the Japanese Occupation.
- 1942-1946: The 6th, 10th and 102nd Infantry Division of the Philippine Commonwealth Army was founded and built on 1942 to 1946 at the military general headquarters around in Lanao province.
- 1942-1946: The 108th Infantry Division of the Philippine Commonwealth Army was founded and built on 1942 to 1946 at the military general headquarters around in Lanao province.
- 1942-1944: Local Christian and Muslim guerrilla groups was founded the invading commands to around the province of Lanao and they aiding the local troops of the Philippine Commonwealth Army units and attacking Japanese troops, Meanwhile, from the couple of three year conflicts and insurgencies by the Japanese troops was retreating by the local Filipino troops and guerrillas and before the liberation.
- 1944-1946: The 10th Constabulary Regiment of the Philippine Constabulary was founded and built on 1944 to 1946 at the military general headquarters in Lanao province.
- 1944: Filipino troops of the Philippine Commonwealth Army and Philippine Constabulary units and the local Christian and Muslim resistance groups was re-invaded the province of Lanao and attacking Japanese troops and before the U.S. liberation forces was returned and entered in the provinces on 1945.
- 1945: Joint military force of the Filipino troops of the Philippine Commonwealth Army and Philippine Constabulary units and the American troops of the United States Army units was liberated in the province of Lanao and aided by the Christian and Muslim resistance and fought against the Imperial Japanese troops and ended World War II.
- 1959-05-22: Lanao province divided into Lanao del Norte and Lanao del Sur through Republic Act No. 2228. Lanao del Sur retained the provincial capital of Marawi (formerly Dansalan).
- 1971-10-04: Meranaw province created from Lanao del Sur through Republic Act No. 6406, remained unorganized due to the disruption caused by the declaration of martial law in the Philippines.
- 1975 Province of Sultan Mardan, Lanao del Sur district two nominated by AFP Governor general Mamarinta Lao in Lanao del Sur.