Simplify the following text for a Grade 7 native English-speaking person.
Original: The Seward Peninsula was once part of the Bering land bridge , a roughly thousand mile wide swath of land connecting Siberia with mainland Alaska during the Pleistocene Ice Age .
Simplified: The Seward Peninsula was once part of the Bering land bridge . This was a strip of land that used to exist that connected Alaska with Siberia with mainland Alaska .