What does the term migtatory workers most closely mean as it is used in paragraph 6?

The term migratory workers most closely mean workers who migrate or move from place to place to pursue work.

Explanation:

"Mexican Migrant Workers in the 20th Century" is an informational text by Jessica McBirney which describes the conditions of immigrants and Mexican Americans throughout the 20th century and how their poor work conditions and low wages are prevalent even today.

The author have used the term 'migratory workers' which most basically means workers who migrates or travels from one place to another to pursue work. Such workers do not have any fixed settlement, they move from place to place in search of work.