While online mapping tools are plentiful, they may not all accurately reflect the true dimensions of your property. The best way to get an accurate representation of your property lines is through a professional site survey.
A professional survey would accurately reflect the dimensions your property. You may either hire a surveyor to locate your property lines and create an accurate map of your property, or contact the Clackamas County Surveyor's Office to see if a survey has been completed and recorded with the County. You may email the Clackamas County Surveyor or call 503-742-4475 to see if a survey of your property has been filed.
OC Web Maps
Oregon City's in-house GIS mapping tool, OCWebMaps, contains maps of the approximate locations of your property lines. While helpful in planning any projects you might have, OCWebMaps is not an accurate substitute for a professional survey by a licensed surveyor.
Oregon City's in-house Plat Finders can help establish certain dimensions that may prove helpful in determining property lines. However, they are not substitutes for a professional survey.