For David Muir, Childhood Dream Comes True In Anchor Chair

There's a new era in network news as David Muir takes over World News Tonight from Diane Sawyer.

Muir is just 40 years old. He wanted to be an anchor since he was a little boy.

He told INSIDE EDITION's Les Trent, "It really is crazy for me to think of the boy from Upstate New York who literally had a dream. I was 12 years old, I typed a letter to the local newsman and I literally went out to the mailbox every single day to see if he would write back."

Watch More of Muir's Interview with INSIDE EDITION

Twenty-eight years later, Muir will now go head-to head against anchors Brian Williams from the first place Nightly News on NBC and CBS Evening News with Scott Pelley.

Muir said, "We have huge admiration for our competition. They put on great, solid broadcasts every night. I always tell the team, 'We don't look sideways. We look straight ahead.'"

At age 40, Muir is the youngest of the big three anchormen. Williams is 55, Pelley is 57.

If things go well for Muir, his run at the anchor desk could last well into the 21st century.

Muir is part of a new generation of anchors who use social media to keep in touch with their audience.

He told Trent, "I hope to be relatable, accessible. Tweet me during the broadcast. Viewers often say, 'Are you tweeting during the commercial beaks?' Of course we are."

Trent said, "You have your phones right there."

Muir replied, "Multiple phones."

On Monday night, Diane Sawyer was part of that TV audience and sent Muir a message during his first broadcast.

Muir said on World News Tonight, "I just want to say 'Thank you' to so many of you for your messages, tweets, so many during the news tonight. And one in particular, from Diane. Thank you friend."

Muir told Trent, "I have been sort of dreaming of this since I was 12 years old. To be able to travel the world with Diane Sawyer and to have her pass the baton to me is a gift I never could imagine."