The Collaborative International Dictionary of English v.0.48:

Caballeria \Ca`bal*le*ri"a\, n. [Sp. See Caballero.]
   An ancient Spanish land tenure similar to the English
   knight's fee; hence, in Spain and countries settled by the
   Spanish, a land measure of varying size. In Cuba it is about
   33 acres; in Puerto Rico, about 194 acres; in the
   Southwestern United States, about 108 acres.
   [Webster 1913 Suppl.]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

CABALLERIA, Spanish law. A measure of land, which is different in different
provinces. Diccionario por la Real Academia. In those parts of the United
States, which formerly belonged to Spain, the caballeria is a lot of one
hundred feet front and two hundred feet deep, and equal, in all respects, to
five peonias. (q.v.) 2 White's Coll. 49; 12 Pet. 444. note. See Fanegas.