Onni Schildt was a senator, manor owner and agricultural advisor. He developed Sysmä and Itä-Häme province with all his heart throughout his life. He e.g. represented his home municipality Sysmä 11 times in the state parliament as a representative of the nobility.
After completing his matriculation in Jyväskylä, Schildt studied law and agriculture in Sweden and Denmark and then settled in Sysmä to manage the 6,000-hectare holdings he had bought and inherited from his parents. He led the Itä-Häme Dairy and Livestock School, which he founded in 1878 in connection with the Hovila manor. Before long, Sysmä was more developed than other municipalities in Itä-Häme in the field of livestock farming.
Onni Schildt was involved in many projects developing Sysmä municipality. He served as supervisor of the municipal board in 1879–1881. He completed the founding project of Sysmä Säästöpankki and served as the bank's manager in 1880–1884 and again in 1886–1913.
Onni Schildt implemented a unique crofter reform in Sysmä and sold 36 farms totaling 3,000 hectares to the highest bidders at an auction. Sysmä became independent before the final release of the crofters, 78 crofts bought with a loan from Sysmä Säästöpankki.
The senator actively participated in the development of Sysmä's care for the poor, healthcare, school, library, and freight and passenger transport. After Onni Schildt's death, the Hovila manor passed into foreign hands after he himself had time to initiate the transaction. The Ilola manor remained in the possession of the heritance.