How can I find the exact boundaries of my property?

You can hire a licensed land surveyor to survey the property and place official markers on the boundary lines. Professional organizations, such as the California Land Surveyor's Association (californiasurveyors.org), often provide useful information on how to choose and work with a land surveyor.

The cost of a boundary survey is determined by the size of the parcel, whether it is in a subdivision, when it was last surveyed, what region of the country it is in, and other factors. A straightforward survey may cost as little as $500 in some areas of the country. But be prepared to spend $1,000 or more if no survey has been done for a long time, if the parcel is large, or if the maps are unreliable and conflicting. In fact, many surveys cost thousands of dollars.

My neighbor and I don't want to pay a surveyor. Can't we just make an agreement about where we want the boundary to be?

You and the neighbor can agree on where you want the line to be and make a "lot line agreement" between yourselves. Then you make it official by signing deeds that describe the boundary. If you decide to do this, make sure you research local zoning and subdivision laws that you may need to comply with.

If you have a mortgage on the property, consult an attorney for help in drawing up the deeds. You may need to get the permission of the mortgage holder before you give your neighbor even a tiny piece of the land.

Once you have signed a deed, you should record (file) it at the county land records office, usually called the County Recorder's Office, Land Registry Office, or something similar.

For more information, check out Nolo's Deeds for California Real Estate, which contains sample deeds, and Neighbor Law: Fences, Trees, Boundaries & Noise, where you'll find more details about boundary agreements and a sample written boundary agreement.