This section is from the book "The Law Of Real Property and Other Interests In Land", by Herbert Thorn Dike Tiffany. Also available from Amazon: A Treatise on the Modern Law of Real Property and Other Interests in Land .
Within the territory ceded to the United States by France, Spain, and Mexico, there existed, at the time of the cession, private rights based upon grants previously made by the nation having dominion therein, and these grants the United States government was, either by express stipulation in the treaty to that effect, or by provisions preserving rights of property, required to recognize.
Though the Louisiana territory was purchased from France, most of the grants made therein before its cession to the United States were made by the Spanish, and not by the French, government, the territory having passed from the former to the latter but a short time previously. The grants made within the limits of the Florida purchase previous to the treaty of cession were expressly recognized in that treaty.
Before the cession of territory by Mexico to the United States, numerous grants had been made by that government from the time of its acquisition of independence from Spain, early in the nineteenth century. Grants made before that period were by the Spanish crown, acting through the governor or viceroy.
In the performance of its treaty obligations to recognize these prior existing grants of land in the ceded territory, this government has adopted the policy of requiring all persons claiming under grants made previous to the particular cession in question to submit their claims to examination either by commissioners named for the purpose, or by the federal courts, and the claims thus submitted have been the subject of many adjudications, frequently of an adverse character.
Lands comprised within the limits of the present state of Texas have been, in succession, the subject of grant by the Spanish government, the Mexican government, the Mexican state of Coahuila and Texas, the republic of Texas, and the present state of Texas.25
23 Am. & Eng. Encyc. Law (1st Ed.) 53 et seq.
25. See Republic of Texas v. Thorn, 3 Tex. 505; Norton v.
Grants made by the previous sovereignties have always been recognized by the present state of Texas.