Last night I was looking through my special shoe box and decided to scan some documents. I have recently discovered a new Poulsen cousin (actually, she found me -- through one of my posts of course), so I was concentrating on Poulsen documents.
So, what is a Desert Land Entry? Well, in March of 1877 Congress enacted the "Desert Land Act" which was designed to foster settlement of the arid and semi-arid regions of the west, specifically in Arizona, California, the Dakotas, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming. The Act allowed anyone to purchase 640 acres of land for 25 cents per acre if the land was irrigated within three years of filing. A rancher could receive title to the land any time within the three years upon proof of compliance with the law and payment of one additional dollar per acre.
Here is an explanation and a table that shows the sales of desert land to June 30, 1890 from Google:
The Public Domain: Its History, with StatisticsBy Thomas Donaldson, United States. Public Lands Commission (1903-1905
Great-grandpa Poulsen's Desert Land Declaration Receipt (first image) doesn't indicate how many acres he was applying for, but 25 cents an acre for a total of $30 comes to 125 acres.
June 22, 1923 he got his $30 back for "Repayment for Lands Erroneously Sold."
If any of your ancestors were farmers in the desert lands, you might want to see if they applied for Desert Land Entries. Check the Records of the BLM.