Steve Inskeep has hosted NPR’s “Morning Edition” since 2004. He is also a popular author and historian, and his latest book “Imperfect Union: How Jessie and John Fremont Mapped the West, Invented Celebrity, and Helped Cause the Civil War” looks at the life of the 19th-century explorer who defined westward expansion, coined the name “Golden Gate” for the strait into the San Francisco Bay, and helped shape the ideas of reinvention and celebrity and give us the legacy of California today.