The communal grazing lands of Alameda heirs and settlers morphed into modern day Rio Rancho primarily through the self-interested efforts of one prominent New Mexican lawyer named Alonzo B. McMillen.
The story is detailed in a juicy 2008 paper in the Natural Resources Journal with the fabulous title: The Blighted History of the Alameda Land Grant: Montoya v. Unknown Heirs of Vigil (pdf). The author, Kristopher N. Houghton, writes a thorough history with the major portion of the story devoted to legal shenanigans and unethical behavior that was not unusual or even considered unethical at the time.
In a move practiced by unscrupulous attorneys, including McMillen himself in Las Trampas, he filed for partition of the Alameda grant, notifying residents and heirs in four newspaper legal ads published in the summer of 1906.
Partition filing at the time meant that any single community member could request the court to divide up the grant lands - including division of the common lands. Because actual division was deemed impossible to do fairly, communal land was sold. And in the case of Alameda, the majority of the grant lands were in communal ownership.
After resolution of the case and multiple appeals it was settled. Claimants got some land in the valley but over 75,000 acres of the communal holdings were sold. The amount was $15,000. After deductions of McMillen's fees and his payment, the amount divided beween the claimants was $8000. Houghton notes the receipts in a court file indicate most Alameda residents got about ten dollars each.
McMillen's "San Mateo Land Company" bought the grant. He had also purchased a great deal of deeded land from claimants during the case, a practice that would get him disbarred today. He ended up with 75,000 acres. The land was sold and leased for ranching until AMREP bought much of it in 1961.