Bonanza

 
Series aired: 1959 - 1973
Video from Internet Archive
 
Primetime TV  
 

The Spanish Grant

Season 1, Episode 21
February 6, 1960
 
Rosita Morales disguises herself as heiress Isabella Marie Inez de la Cuesta in an attempt to gain possession of a land grant which has part of the Ponderosa in it. Ben becomes suspicious and with his sons tries to track down the real heiress.  
Bonanza
Available on DVD