KANSAS CITY -- An estimated crowd of 800,000 Royals fans packed downtown Kansas City two days after the Royals sewed up their first World Series championship in 30 years in Queens, N.Y., in 2015. Closer Wade Davis, waiting to hop on stage for the celebration at Union Station, peered at the incredible sea of blue.

“It is,” Davis said, “breathtaking.”

The seeds for that championship were actually planted a year earlier, when the Royals lost a heartbreaking Game 7 in the World Series to the Giants. While most Royals fans were deliriously happy that the Royals had made it to their first World Series in 29 years -- and were simply relevant again -- the Royals themselves were anything but satisfied.

“It’s great to know you won the American League championship and you got to play in the World Series,” veteran Alex Gordon said at the time. “But it is still hollow that you got that close and didn’t win it all. None of us feel good about that.”

Thus, the 2015 season became known as the Royals' "Unfinished Business Tour."

It started in the 2014-15 offseason, when general manager Dayton Moore and his staff aggressively signed numerous free agents, including pitchers Edinson Vólquez, Ryan Madson and Chris Young, as well as slugger Kendrys Morales. The signings were an uncanny success; nine of them contributed to the 2015 success, most in significant fashion.

“It gave us a lot of confidence, knowing how aggressive the front office was,” Gordon said. "No one was satisfied.”

The Royals certainly hit the ground running in Spring Training. They plowed through the Cactus League, winning 20 of 30 games.

“You look in their eyes,” manager Ned Yost said then, “and you see hunger and determination.”

The Royals roared out of the gate in the regular season as well, winning their first seven games and outscoring their opponents 52-18. They were soon in first place in the AL Central with a 15-7 mark.

The Royals also were proving to the world they weren’t about to take any shots from opponents. An April series with the A’s at Kauffman Stadium featured an almost playoff-like intensity -- it was Oakland’s first trip back to Kansas City since its painful Wild Card loss there in 2014.

Oakland’s Brett Lawrie slid hard with spikes up into shortstop Alcides Escobar at second base in the Friday game, injuring Escobar. The Royals retaliated when Yordano Ventura hit Lawrie with a pitch on Saturday, and when Kelvin Herrera threw a 100-mph fastball behind Lawrie on Sunday.

The series featured benches clearing, a lot of angry words and two wins by the Royals. Privately, the Royals’ coaching staff was proud of its players sticking up for each other.

Publicly, Yost said, “A lot of this is probably my fault because these kids have never been through this. And it’s my job, and it’s our job, to teach them how to deal with these situations. But we’ve never been confronted with these situations. So it’s actually been a good thing for us.”

There were other positive signs galore. Mike Moustakas, who had resurrected his career with an amazing 2014 postseason, was hitting .320 with an .855 OPS through May. Morales was hitting .304 with 38 RBIs through the first two months. And the back end of the Royals’ bullpen continued to be stellar, with power arms Luke Hochevar and Madson added to the deadly trio of Herrera, Davis and Greg Holland (who, as we learned later, was pitching with a torn UCL).

There was plenty of fun to the 2015 season as well, including the All-Star Game in Cincinnati in July. At one point, the Royals had eight players leading in the balloting, instigating cries of ballot stuffing by Royals fans throughout baseball. The Royals wound up with seven All-Stars, and the American League won the game managed by Yost, which assured the AL pennant winner home-field advantage in the playoffs.

Still, even as the Royals remained in first place for 53 straight days in June and July, Moore and his staff felt a need for additions as the Trade Deadline approached. Earlier that month, Gordon was placed on the injured list with a left groin strain, and the Royals knew it would be a lengthy stint. Second baseman Omar Infante, who had a solid first season with the Royals’ in ’14, was hitting .233 with a woeful .567 OPS as July wound down.

Vólquez pleaded for Moore to pursue his friend, Johnny Cueto, to bolster the rotation. And as luck would have it, the A’s, fading fast at the Deadline at 14 games under .500, were willing to move super-utility man Ben Zobrist, a pending free agent.

“As good as our offseason deals came to be,” Moore said, “I don’t think we win it without getting Cueto and Zobrist.”

Zobrist immediately took over in left field for Gordon, then replaced Infante at second base when Gordon returned in September.

Cueto had his ups and downs in the regular season, but came up big in the postseason. Cueto sealed the AL Division Series against the Astros with an eight-inning, two-run effort in Game 5. He then turned in a one-run, complete-game effort in the World Series Game 2 win over the Mets, allowing just two hits.

The fightin’ Royals appeared to return in August during a trip to Toronto, a preview of the intensity the two teams would display in the AL Championship Series two months later. On a Sunday getaway day on Aug. 2, the Royals and the Blue Jays emptied benches repeatedly when the Blue Jays’ Josh Donaldson perceived that Vólquez was throwing at him.

The war of words between the teams continued after the game through the media and Twitter. Vólquez said of Donaldson, “He cry like a baby.”

The Royals surged in July and August. By Aug. 29, they were 80-49 with a 14-game lead in the AL Central. Clinching a division title was a foregone conclusion, and that came on Sept. 24 with a 10-4 victory over Seattle. The Royals stumbled a bit in mid-September but won their final five games to sew up home-field advantage throughout the postseason.

And all of that set up these iconic postseason moments that will live forever in Royals lore:

• Down 6-2 in the eighth inning at Houston in Game 4 the ALDS, the Royals pulled off a near miracle with a five-run, season-saving rally and eventually won, 9-6, to set up a Game 5 clincher in Kansas City.

• The Royals captured the pennant by beating the Blue Jays in six games. Game 6 was one for the ages, featuring Lorenzo Cain scoring from first on a single to right by Eric Hosmer. Davis pitched in the eighth, sitting out a lengthy rain delay, then returned to pull off a Houdini act in the ninth to seal a trip to the World Series.

• Gordon homered off Jeurys Familia in the ninth to tie the score against the Mets, and the Royals won Game 1 of the World Series in extra innings.

• Hosmer’s “Mad Dash” home tied the score in the ninth in Game 5, and Christian Colón, in his only postseason at-bat that fall, singled home the go-ahead run in extras as the Royals won, 7-2, to take the World Series title.

The championship was extra special for Vólquez and Young, both of whom lost their fathers in 2015; Young’s father died in late September, while Vólquez learned of his father’s passing after Game 1 of the World Series.

“It’s an experience we’ll never forget,” Vólquez said. “I think we had some help from above.”