Whether the United States has fulfilled its obligations under the 1848 Treaty of Guadalupe Hidalgo, with respect to property rights held by traditional communities in New Mexico, has been a source of continuing controversy for over a century. The controversy has created a sense of distrust and bitterness among various communities and has led to confrontations with federal, state, and local authorities. Under the Treaty, which ended the Mexican-American War, the United States obtained vast territories in what is now the U.S. Southwest, from California to New Mexico. Much of this land was subject to pre-existing land grants to individuals, groups, and communities made by Spain and Mixico from the 17th to the mid-19th centuries, and the Treaty provided for U.S. recognition and protection of the property rights created by these grants. The effect of this alleged failure to implement the treaty properly, heirs contend, is that the United States either inappropriately acquired millions of acres of land for the public domain or else confirmed acreage to the wrong parties. According to some heirs, the resulting loss of land to grantees threatens the economic stability of small Mexican-American farms and the farmers' rural lifestyle. In response to a request by congressional members, this report: (1) describes the confirmation procedures by which the United States implemented the property protection provisions of the 1848 Treaty of Guadalupe Hidalgo with respect to community land grants located in New Mexico, and the results produced by those procedures; (2) identifies and assesses concerns regarding these procedures as they pertain to the government's confirmation of these grants from 1854 to 1904; (3) identifies and assesses concerns regarding acreage transferred voluntarily or involuntarily after the confirmation procedures were completed; and (4) identifies possible options that Congress may wish to consider in response to remaining community land grant concerns.