In 1999, St. Charles County adopted the Unified Development Ordinance (UDO) (zoning and subdivision ordinance) which developed out of the land subdivision regulations that had been in place since 1959.

Chapters
The UDO consists of the following Chapters of the Ordinances of St. Charles County (OSCCMo):

• Chapter 405: Zoning Regulations
• Chapter 410: Subdivision Regulations
• Chapter 412: Erosion and Sediment Control Regulations

The Department of Community Development makes the UDO along with the following chapters of the OSCCMo available as a single document:

• Chapter 415: Preservation of Highway Corridors
• Chapter 417: Directional and Way-Finding Signage
• Chapter 420: Miscellaneous Regulations Concerning Land Use
• Chapter 422: Model Illicit Discharge and Connection Regulations
• Chapter 425: Fees