| image = [[File:Flood Damage in Dayton, Ohio.jpg]]
| caption = View of damage on Third Street in Dayton, Ohio after
flooding, March 25, 1913. Heavy rains during Easter week in March 1913 caused flooding across Ohio. Businesses and railroads suffered more than $300 million of damage, over 20,000 homes were destroyed and 428 Ohioans were killed. The most damage occurred in the Miami Valley area, particularly the city of Dayton.
'Orr v. Allen '' was an important legal case heard by the United States Supreme Court that upheld the right of a state to use the power of eminent domain to advance public welfare. The state of Ohio passed the Ohio Conservancy Law, also known as the Vonderheide Act, after the Flood of 1913. This flood is known as the greatest natural disaster in Ohio history. Although rivers in Ohio tended to flood every spring, heavy rains in March 1913 exacerbated the flood conditions. Most communities located along rivers in the state experienced flooding, even those that had not had problems in the past. The most severe flooding occurred along the Great Miami River, and the conditions in Dayton were particularly bad. When the flood was over, Ohioans began to assess the damage. At least 428 people died during the Flood of 1913, and more than twenty thousand homes were totally destroyed. Property damage was extensive, as many other homes were seriously damaged. Factories, railroads, and other structures also faced major losses. After the flood waters receded, Dayton residents were determined to prevent a future disaster of this magnitude. They hired hydrological engineer Arthur Morgan to come up with an extensive plan to protect Dayton from floods. Morgan recommended the construction of a series of earthen dams on the Great Miami River, as well as modifications to the river channel in Dayton. Governor James M. Cox supported the plan, helping to gain passage of the Ohio Conservancy Law in 1914. The law gave the state the authority to establish watershed districts and to raise funds for improvements through taxes. Some Ohioans opposed the law, ultimately challenging it in both the state and United States supreme courts in ''Orr v. Allen '' (1915 and 1919). They were concerned that the projects would be funded by taxing those who would benefit from the improvements rather than by taxing all residents of the state. In addition, the law allowed districts to seize land through eminent domain. Both the state and United States supreme courts upheld the Ohio Conservancy Law.[[Category:History Events]] [[Category:The Progressive Era]]