Sources: They do conflict, so welcome to the fun!

Modern:

Old Spanish Measures:

    The Spanish system of measures contained the following units - there were many more than those we list here.  The official Spanish vara de Burgos (or vara de Castilla) was set by royal Spanish edict in 1801 and measured 0.8359 meters (32.909 inches). 

Mexican California 1840's:

    The official vara had 22 accepted variations in California prior to the Treaty of Guadalupe-Hidalgo of 1847, which set the vara at 33 inches.  New variations upon 33 inches arose in south-west US until 1855 when the Texas vara was set at 33.333 inches.

US California 1850+:

    Deeds and survey maps used the following survey measures, still in use today:

Argentina 1835, pre-metric:

    In 1835, the Argentine system of distance & length measures recognized the following units:

    In Santa Fé, the shorter vara de Bustinza was an accepted alternative to the official measure.

Modern:

Mexican California 1840's:

    Please bear in mind that many survey maps of the early 1800's were estimates made without benefit of proper measurement, e.g. California diseños (survey maps) of the 1840's were often made a ojo (estimated by eye).  The 2.6% maximum variance in the standard Mexican land measure of the 1840's, sitio de ganado mayor, pales in comparison to the huge errors in mapping and translation - witness the legal problems Wilhelm's inaccurate diseño (made a ojo from the back of a horse) caused the subsequent owners of Rancho Herman.

Sitio de Ganado Mayor:  During the first half of the 1800's in Mexico, of which California and Texas were part, large land grants were measured in sitios de ganado mayor (or sitios) - often translated into English as leagues without proper qualification.  Originally one sitio de ganado mayor was the amount of land considered necessary for a cattle ranch, however, land grants most often consisted of several sitios de ganado mayor.  A sitio de ganado mayor was a square of 5,000 x 5,000 varas.  Simple enough, except that the length of the vara varied over time and place - see above.  It was also considerably smaller than the Spanish or Argentine legua (of 6,666.7 or 6,000 varas per side respectively). 

Fanega de Sembradura:  The highly inexact area sown by a fanega of seed - varies by place, year, person, and seed sown: corn (0.6 - 8.8 acres) or wheat (0.15 - 1.8 acres).  The sizes in the above table were used by Governor Vallejo for wheat sown at Fort Ross in 1841.

Argentina 1835, pre-metric:

Cuadra: Crop yields and land prices were often quoted in cuadras until about 1950.  (To further confuse crop yields, it's possible they used the old quintal of approx.  46 kg. and not  the metric quintal of 100 kg.!)

Legua: In  Argentina, the size of estancias (aka: camps or ranches) are often broadly described in leguas de campo or leagues of land.   In modern terms, a legua or league is a metric square league - we include it here for easier comparison.  

Suerte de estancia: An old term not currently in use. 

Modern: