The Houston native's enthusiasm for playing with the Astros have helped lift the spirits of their fans, who feel like their team now has a future.
Appel, the No. 1 overall pick in this year's First-Year Player Draft, was part of a press conference at Minute Maid Park that introduced him to the Houston baseball community.
"Growing up in Houston I came to games at the Astrodome and at Minute Maid," Appel said. "That was the dream. It was every kid's dream to play for your home team and now it's a reality. It's still surreal. I don't think it's sunk in."
While terms were not announced, it is believed Appel received a $6.5 million signing bonus. The contract also carries a provision that he will be invited to spring training in February.
Astros general manager Jeff Luhnow, who drafted shortstop Carlos Correa with last year's No. 1 pick instead of Appel, called it a "significant investment."
Appel grew up an Astros fan. He started his baseball career in Houston as a Little Leaguer. He moved to the East Bay at the age of 12.
"It's been quite the road and I guess I'm home," Appel said. "It's an honor be here. So many emotions are running through me right now."
When the Astros passed on Appel last year, the Pittsburgh Pirates selected him with the eighth overall pick. Appel turned down a $3.8 million offer and returned to Stanford for his senior year, where he was 10-4 with four complete games and a 2.12 ERA. He recorded 130 strikeouts in 106 1/3 innings and held opponents to a .203 batting average.
Appel, the Pac-12 Baseball Scholar-Athlete of the Year, finished as Stanford's all-time strikeout leader with 372. He's sixth in school history with 28 career wins and fourth with 377 2/3 innings pitched.
"Drafting and signing Mark Appel was a top priority for our organization this year," Luhnow said. "We are an organization focused on winning championships in the future and we expect Mark to be a big part of that effort."
Appel reports to extended spring training, along with all other signed draft picks and free agents, at Houston's spring training facility in Florida next week. His first destination appears to be at short A Tri-City.
The Astros have signed 23 of their 40 draft picks this season, including seven of their top 10.
If Appel shows he's ready, he could move quickly up the organizational ladder, possibly finishing the season at Double-A Corpus Christi.
"This is what we believe is going to be a high-impact addition to our organization," Astros' amateur scouting director Mike Elias said. "He is someone who has the potential to be a front-line starting pitcher for a very long time."
Stanford grad Jason Castro is Houston's starting catcher. Stanford players Brian Ragira (San Francisco Giants) and Austin Wilson (Seattle Mariners) also have signed.
Stanford's Lonnie Kauppila (Seattle), Garrett Hughes (San Francisco), and Justin Ringo (St. Louis Cardinals) are unsigned.
Palo Alto High grad Tyger Pederson is also unsigned.