How can I determine cost basis for land inherited in 1976

[Critter]

Historical values may be had thru the property tax rolls or you may seek help from a local realtor.

[SweetieJean]

. Generally, when property or other assets are inherited, the cost basis is usually equal to the fair market value of the property or asset at the time of the decedent's death.

[Carl]

THe county courthouse will have historical records on the property. If there was an actual sale of the property 2 years either side of the date of the passing of the person you inherited it from, you can use that price as your cost basis. Otherwise, you'll need to consult with a realtor or tax pro whose been around for awhile.

[Opus 17]

Consult a real estate agent or a licensed appraiser.  An appraiser can use historical sales records to determine a retroactive value.

Vacant land may be difficult to value because so much is based on speculative future uses.  Farmland is often quite easy, there will be reliable values for cost per acre of productive farmland.  Other situations may be in between.  

The key point is to make a diligent good faith effort to establish a value.  If you are unlucky enough to get audited, the IRS won't give you any basis that you can't back up with pretty good proof.