Simplify the following text for a Grade 7 native English-speaking person.
Original: The Smithsonian Institution developed its network of observers over much of the central and eastern United States between the 1840s and 1860s once Joseph Henry took the helm .
Simplified: In the 1840s , Joseph Henry took charge . He helped the Smithsonian Institution focus most of its observers on the center and the eastern part of the United States during the 1840s and 1860s .