Simplify the following text for a Grade 9 native English-speaking person.
Original: In 1861 the outbreak of the American Civil War cut off supplies of cotton to the mills of the north west of England and as a result a number of prosperous mill owners looked for new business opportunities to diversify their interests .
Simplified: In 1861 the outbreak of the American Civil War cut off supplies of cotton to the mills of the north west of England . As a result a number of prosperous mill owners looked for new business opportunities to diversify their interests .