Complex sentence: Two of DeKalb's most prominent citizens, Jacob Haish and Isaac L. Ellwood, each promised to donate $20,000 to help absorb some of the new building's cost; their donation hinged upon the courthouse being moved to and constructed in DeKalb.
Split into simpler sentences: Two of DeKalb's most prominent citizens, Jacob Haish and Isaac L. Ellwood, each promised to donate $20,000 to help absorb some of the new building's cost. Their donation hinged upon the courthouse being moved to and constructed in DeKalb.