Simplify the following text for a Grade 9 native English-speaking person.
Original: The International Opium Convention , signed at The Hague on January 23 , 1912 during the First International Opium Conference , was the first international drug control treaty .
Simplified: The International Opium Convention was the first drug control treaty ( or agreement ) . It was signed at The Hague in The Netherlands on January 23 , 1912 .