Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_name_52 (year INTEGER, league VARCHAR)
### Question:
What was the earliest year for the USISL Pro League?
### Answer:
SELECT MIN(year) FROM table_name_52 WHERE league = "usisl pro league"