Misty of Chincoteague
Marguerite Henry

Maureen and Paul live with their Grandma and Grandpa Beebe on their pony farm on Chincoteague Island. The wild ponies that live on Assateague are rounded up for sale in July and Maureen and Paul had their hearts set on keeping Phantom, the mare that had eluded capture for two years. When they found Phantom, she had a foal that they immediately named Misty.