Complex sentence: "Hush, Little Baby" is a traditional lullaby, thought to have been written in the United States (mockingbirds are from the New World), but the author and date of origin are unknown.
Split into simpler sentences: Hush, Little Baby is a traditional lullaby. It is thought to be written in the United States (mockingbirds are from the New World), but the author and date of origin are unknown.