Simplify the following text for a Grade 4 native English-speaking person.
Original: A. M. Elgin opened the first coal mine in the Mystic area in 1857 , about 1.5 miles north of Mystic on Little Walnut Creek .
Simplified: A. M. Elgin opened the first coal mine in the Mystic area in 1857 . It was about 1.5 miles north of Mystic on Little Walnut Creek .