Identify the county of the residence in question, find the county's homepage online and scroll through their department listings until you find the assessor's office. This office may have a webpage within the county's website, or you may be directed to a separate site. Find the assessor's search tool, which is usually under "assessment information," "property information" or a related link.
Search for the property using the information you have. A parcel number makes the search easy, but you may also be able to use a street address or the owner's first and last name. Enter the information in the search field and continue.
Search the results until you find the intended property. An address or parcel number should yield the specific house you're looking for, however, if you used an owner's name, and it's a common name, or the owner has multiple properties, you may have to scroll through several listings until you find the right property.
Review the parcel information and find the original year of construction, usually next to "Year Built" or like terms. The home's profile page also features data such as acreage, zoning, square footage and rooms in the house. Within this list of characteristics, you can find the original year of construction and an effective date. The effective year is that in which permitted construction, major remodeling or additions to the house were made.