Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_75876 ( "Rank" real, "Main span metres" text, "Main span feet" text, "Year opened" real, "Country" text )

### Question ###
What is the main span feet from opening year of 1936 in the United States with a rank greater than 47 and 421 main span metres?

### Accurate SQL ###

SELECT "Main span feet" FROM table_75876 WHERE "Year opened" = '1936' AND "Country" = 'united states' AND "Rank" > '47' AND "Main span metres" = '421'