For the longest time, we thought about the horse racing’s Triple Crown in terms of the impossible. During a 59-year span from 1919 to 1978, 11 horses were able to win the Kentucky Derby, Preakness Stakes, and Belmont Stakes in the same year. That meant an average of once every five to six years, a Triple Crown title was earned.

And then came the drought after Affirmed last completed the feat in 1978. A decade. Two decades. Three decades. Anyone younger than their mid-40s or so in age had no real evidence the Triple Crown had ever been winnable except some fuzzy videos, likely from before when they were born.

And then in 2015, American Pharoah made the impossible possible. Horse racing didn’t hold the same place in American hearts by then as it once had. But still, it captured attention for at least a few minutes when Pharoah made his historic run at the Belmont. People tuned in to their televisions, streamed it online, and even watched it on the video boards of stadiums.

Finally. It can be done!

2016 reminded us why it took so long between achievements, when Nyquist, Exaggerator, and Creator split the three Triple Crown races. But now we turn our attention back as a fresh Triple Crown season begins. Can Pharoah’s half brother by the same father, Classic Empire, repeat? Will another horse, maybe McCraken, maybe Always Dreaming, maybe another we haven’t even thought of, make a run?

So far 35 horses have taken the first two jewels of the Triple Crown. Twenty-three failed to win the third one. However in 2017, we again went without a winner. Always Dreaming won the Kentucky Derby, but two weeks later could not duplicate the effort, as Cloud Computing took home the victory.

The potential that any year could be the year, that any horse could be the horse, is part of what makes this so fun. With that in mind, let’s answer all your burning questions.

What is the Triple Crown?

Thoroughbred horse racing is a sport that can be found in some form for 12 months of the year, with the reason for its existence to entice gamblers to put money on a horse. But three races pique the imagination more than most: the Kentucky Derby, the Preakness Stakes and the Belmont Stakes.

Those three are known as the jewels of the Triple Crown, and they are run on dates ranging from the first Saturday in May through early June. People who might not pay attention to horse racing the other 49 Saturdays of the year will tune in, throw a party and make their picks, whether they know anything about the horses or, more likely, not.

Why should we care?

It's a fair question to ask. Why do we even care about the Triple Crown? Horse racing is known as "the sport of kings." It's expensive to get into as an owner — one of the Belmont Stakes entrants is owned by the ruler of Dubai. It's expensive to attend the races. And if you're a gambler with a bad tip, it can be expensive to your wallet, too.

Yet every May, the Kentucky Derby is one of the most-watched sporting events of the year. And if the Derby winner wins the Preakness two weeks later, his name is one you hear again and again, in media and casual conversation both.

Horse racing might not have the widespread appeal it did in the 1930s — remember the movie Seabiscuit? — but the spectacle of seeing the Triple Crown won for the first time in nearly 40 years makes for pretty compelling drama. You might not have any connection to the sport, but you still want to see if it's finally going to be done. Plus, it's pretty fun to make your pick and see two minutes later whether you were right or not.

How many horses have won the Triple Crown?

Twelve. Sir Barton (1919), Gallant Fox (1930), Omaha (1935), War Admiral (1937), Whirlaway (1941), Count Fleet (1943), Assault (1946), Citation (1948), Secretariat (1973), Seattle Slew (1977), Affirmed (1978), and American Pharoah (2015).

How long have we tracked the Triple Crown?

The races have been around since the 1800s, but the term "Triple Crown" wasn't used widely before Charles Hatton of the Daily Racing Form began to use it regularly in the 1930s, although it had been around since 1923. And interestingly, the Preakness was actually held before the Kentucky Derby 11 times before 1931.

No trophy for the accomplishment existed before one was commissioned in 1950.

What races make up the Triple Crown?

The three jewels in the crown:

• The 1-1/4-mile Kentucky Derby, which is run the first Saturday in May at Churchill Downs in Louisville. Up to 20 horses (with four also-eligible alternates) can enter.
• The 1-3/16-mile Preakness Stakes, which is run the third Saturday in May at Pimlico Race Course in Baltimore. Up to 14 horses (with two also-eligible) can enter.
• The 1-1/2-mile Belmont Stakes, which is run the third Saturday after the Preakness at Belmont Park in Elmont, N.Y. Up to 16 horses can enter.

All three are listed as Grade 1 (the highest level) and are open only to 3-year-old horses.

How does a horse become Triple Crown eligible?

The Kentucky Derby is the key. Horses earn their way in through a series of races called "The Road to the Kentucky Derby." The goal is to get as many points as possible during their 2-year-old and 3-year-old races. For the 2015 Derby, there were 19 races offered in the Kentucky Derby Prep Season and another 16 in the Kentucky Derby Championship Season. The latter is the key one, with the most points available. Horses that gain entry to the Derby typically run in three to six races from the autumn through the spring before the Derby. The field that qualifies for the Kentucky Derby are then the Triple Crown-eligible horses and can enter any of the three races.

So why is the Triple Crown so hard to win?

Take your pick of theories here. It's probably a little bit of each of them:

• Winning all three races requires running in all three races. This is not a common practice. After 20 horses entered the Kentucky Derby this year, only eight were in the Preakness and only eight will be in the Belmont. In 2015, American Pharoah was the only horse to enter all three. What that means is that most, if not all, horses competing against a horse trying to win the Triple Crown have fresher legs by the time they reach the Belmont.
• With so much money, both in acquiring the horse and in breeding income after its racing career, being cautious is the name of the game. Why risk a horse breaking down with so much money invested in it? In 2012, I'll Have Another didn't compete after winning the first two jewels of the crown, due to injury.
• The Belmont is a 1-1/2-mile track. That makes it the longest stakes race any of the horses will enter in North America. So not only is the horse that wins the first two jewels of the Triple Crown going on less rest, it's tasked with running in the longest race of its life to ultimately win the honor. And yes, that extra quarter mile does make a difference.
• Horses aren't bred for the Belmont. The goal every year is to gain entry into the Kentucky Derby. So sprinting is more important to have in the bloodline than endurance. The 1-1/2-mile Belmont weeds out the horses with peak speed that is best for the shorter Derby or Preakness.