Las Siete Partidas is the major law code of 13th century Spain, compiled under the reign of Alonso x of Castile (1252-1284), and considered to be the greatest achievement of "Alfonso the Wise." The Castilian civil code drew from many sources: Roman and Canon law, Islamic law and Visigothic codes, as well as the writings of Aristotle and Seneca. The Seven books of the Partidas form an acrostic, each book begins with a letter of the name 'Alfonso':

A seruicio de Dios... (For the service of God...)

L a ffe catholica... (The Catholic faith...) 

F izo Nuestro Sennor Dios... (Our Lord God did...)

O nras sennalades... (Special rites...)

N ascen entre los ommnes... (Among men there arise...)

S esudamente dixeron... (The ancient wise men sagely say...)

O luidanca et atreuimiento... (Forgetfulness and boldness...)

Las Siete Partidas del sabio rey don Alonso ed Nono... nuevamente glosades, por el licenciado Gregorio Lopez. Madrid : Juan Hasrey, [1610-1611]. 

Compiled during the Reconquista, Las Siete Partidas prioritized the resettling and holding of Iberian frontier lands. The Partidas are believed by many scholars to be an attempt to unify the Kingdom's legal system during a period of transition. Although the Partidas are greatly influenced by Justinian law and canon law, they also draw from Islamic law, and, particularly relevant in terms of the rights of women, Visigothic law codes, which made provision for community property within marriage. Unique among European and English legal systems of the time, Las Siete Partidas decreed a woman's right to hold property in her own name, independent of male relations, along with many other legal rights and responsibilities for women viewed as progressive even into the mid-nineteenth century, when portions of the Siete Partidas were passed into Texas statutory law.

Tarlton holds two editions of the four-volume 1610 Madrid imprint of Las Siete Partidas, with the text in Castilian Spanish and the surrounding commentary in Latin, although the Titles 3-7 and the Repertorio of the second set were most likely from the 1587 Vallodid imprint. The second set of Siete Partidas was given to Tarlton by early University of Texas law professor Robert Lynn Batts, whose signature can be seen on the title page of the first volume.