The “Timber Culture Act” was pass in 1873 and was intended to encourage the planting of trees in Great Plains and western parts of the United States. In some places it worked as intended and in others it did not. The requirements to obtain land under the Act changed over time, but always centered on planting trees on a requisite number of acres.
In some areas settlers or others completed their timber claims and obtained title to the land–generating a patent that transferred title to the property. In many other areas claims were not completed, either because the land simply was not suited to grow timber or the claimant was trying to gain use of the land for a time. Incomplete, relinquished, or abandoned timber claims would not have generated a patent because title was never transferred to the claimant.
Patents transferring land for completed claims are on the Bureau of Land Management website. The application files are at the National Archives. Incomplete claims did not generate a patent. Those files are at the National Archives as well, but the researcher would need to know the location of the claim in order to locate the record. Timber claim files generally do not contain quite as much genealogical information as do homestead files.
There’s more information on timber claims in this article on the Minnesota Historical Society website.