It was in the mid-1860s that the San Joaquin River and its surrounds underwent the greatest change they had seen in human history: the introduction of irrigated agriculture. As early as 1863, small irrigation canals were built in the Centerville area, southeast of Fresno, but were destroyed in subsequent floods. The vulnerability of the small local infrastructure led to the establishment of irrigation districts, which were formed to construct and maintain canals in certain areas of the valley. One of the first was the Robla Canal Company in the Merced River area, which went into operation in March 1876, but was soon surpassed by the Farmers Canal Company. The district built a diversion dam on the Merced, sending its water into a pair of canals still in use today.