Simplify the following text for a Grade 4 native English-speaking person.
Original: In 1877 , he opened a flour mill at the nearby Watab River , and in 1884 he started the Sartell Brothers Lumber Company with his sons .
Simplified: In 1877 , he started a flour mill at the nearby Watab River . In 1884 , he started the Sartell Brothers Lumber Company with his sons .