You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Multiracial_American

Context:
In Virginia prior to 1920, for example, a person was legally white if having seven-eights or more white ancestry. The one-drop rule originated in some Southern United States in the late 19th century, likely in response to whites' attempt to maintain white supremacy and limit black political power following the Democrats' regaining control of state legislatures in the late 1870s. The first year in which the U.S. Census dropped the mulatto category was 1920; that year enumerators were instructed to classify people in a binary way as white or black. This was a result of the Southern-dominated Congress convincing the Census Bureau to change its rules.

Question:
What year was mulatto left off the US Census?

1920