Note: Snohomish County Assessor records often have the wrong built date.
The city's interactive map has access to historic permits
where you can often find the age of the house and its first owner or builder.
This is a fantastic research tool.
To use: First, press the circled "i" icon near the upper right.
Zoom in and click on a property.
Then click on one of the LaserFiche records.
Often you'll find water records with the owner's name, and the date the water was turned on.
Usually that's when the house was complete.
This can often be verified in the Everett Public Library's Northwest Room, using the Polk Directories and many other resources.