As Zenyatta looks for her 17th consecutive victory tonight, here's a quick look at those she will be trying to best in the history books.

Citation

Citation gave notice early that he would be a star. The champion 2-year-old and 2-year-old colt of 1947, he won 12 of his first 13 career starts in 1947-48, with the only loss in that span coming by a neck to eventual champion filly Bewitch. Following a rough trip that over a poor track that resulted in a loss to longshot Saggy in the Chesapeake Trial, Citation, with Eddie Arcaro aboard, kicked off his win streak in some of America's most prestigious events.

He rebounded from his loss by capturing the Chesapeake Stakes five days later, on April 17, 1948. In another quick turnaround, more common for horses of his era, he won the Derby Trial on April 27, then the Kentucky Derby on May 1. After taking the Preakness, Citation made a quick side trip to New Jersey to take the Jersey Derby before winning the Belmont, becoming the eighth horse to sweep the Triple Crown.

That summer, he won the Stars and Stripes Handicap against older horses, an allowance race, the American Derby and then the Sysonby Mile to run the streak to 10. He won the two-mile Jockey Club Gold Cup at Belmont in early October, then two weeks later, won the similarly-named mile and five eigths Gold Cup (also known as the International). Thirteen days later, no horses could be found to challenge Citation, who won the Pimlico Special in a walkover.

It was off to California for the remainder of the 1948 season. Citation won an allowance race at Tanforan on Dec. 3, then captured that track's signature event, the Tanforan Handicap, by five lengths on Dec. 11. But that would be his last trip to the starting gate for a long time, as he emerged from the win with an osslet, a stress injury.

Citation would make his return to the races exactly 13 months later, winning an allowance at Santa Anita on Jan. 11, 1950. But the win streak would come to an end just 15 days later, as Miche, carrying 114 pounds to Citation's 130, would edge the champion by a neck in a handicap at Santa Anita.

Altogether, Citation's win streak included victories at nine different tracks, ranging at distances from six furlongs to two miles. The most weight he car¬ried during the streak was 126 pounds, six times - although to be fair, the majority of his streak came as a 3-year-old, with 126 being the classic impost for that division. Arcaro was aboard for all but two of the wins.

Citation retired in 1951 as rac¬ing's first millionaire, with earn¬ings of $1,085,760, and a career mark of 45-32-10-2. Remarkably, his record includes 22 stakes wins and eight runner-up efforts. For that brilliant 1948 season, he was named Horse of the Year, champion 3-year-old, champion 3-year-old colt and champion handicap horse. He was inducted into the National Racing Museum’s Hall of Fame in 1959.

Mister Frisky

Mister Frisky, a Florida-bred, began his career in Puerto Rico, where he set the tracks on fire by winning his first 13 races. This included victories in prestigious stakes in that country, such as the Clasico Santiago Iglesias Pantin and Clasico Juan Orlando Herrero. He also won the Clasico Dia de Reyes by 10 lengths, breaking the track record for seven furlongs. Overall, he set two track records and equaled another at El Comandante.

The brilliant colt was then brought to the United States in early 1990 to see if he could make a run at the Triple Crown events. He ran roughshod over his opponents in the California prep races, scoring victories in the San Vicinte Stakes, San Rafael Stakes and Santa Anita Derby to stamp himself as the favorite for the Kentucky Derby.

But Mister Frisky, bringing that 16-race win streak into Kentucky, finished eighth behind Unbridled, then third behind Summer Squall in the Preakness. A few days later, an abscess was found in his esophagus, an issue believed to be at least partially responsible for those losses.

Mister Frisky would recover from the medical problem and returned the following year to finish third in a sprint at Del Mar and second in an allowance to the Belmont winner Go And Go. A member of the Puerto Rican Hall of Fame, he concluded his career with a record of 20-16-1-2.

Cigar

Unlike Citation and Mister Frisky, Cigar didn't flash many early hints of his future stardom. Despite breaking his maiden on the main track, the son of Palace Music competed on the turf for much of his early career, winning just once in 11 starts. He was transferred to trainer Bill Mott in 1994, who eventually moved him back to the dirt. Cigar signaled his affinity for the surface by winning an allowance at Aqueduct by open lengths on Oct. 28, 1994. From there, it was straight to the Grade I NYRA Mile (a race even¬tually renamed in his honor), which he also won by daylight.

The big bay would return in 1995 to run a perfect 10-for-10 campaign. He began by taking an allowance at Gulfstream Park, then back-to-back Grade Is there in the Donn and the Gulfstream Park Handicap. His next four starts all came against stakes company at different tracks, in the Oaklawn Handicap, Pimlico Special, Massachusetts Handicap and Hollywood Gold Cup.

Then it was home to New York in the fall, where he won the Woodward and Jockey Club Gold Cup. He finished the campaign with a smashing victory in then-record time in the Breeders' Cup Classic over a muddy Belmont strip.

The 1995 campaign earned Cigar his first Horse of the Year title, as well as Eclipse champion older male, but with the streak at 12, he returned as a 6-year-old for one more season. He began with a second edition of the Donn. Then it was halfway around the world to run in the inaugural Dubai World Cup, at Nad al Sheba in the United Arab Emirates. Despite missed training time leading up to the race, Cigar gallantly held off fellow American Soul of the Matter to win.

Cigar then won a second edition of the Massachusetts Handicap. His 16th straight win came in the Arlington Citation Challenge, a special stakes event carded by Arlington Park in Chicago, on July 13, 1996.

But a month later, on August 10, the streak ended, as Dare of Go defeated Cigar, who was softened up by a hot early pace, in the Pacific Classic. Cigar’s streak had lasted nearly 14 months and had taken him to nine tracks, in seven states and Dubai, carrying weights of up to 130 pounds.

Cigar would retire that fall with a lifetime record of 33-19-4-5 (22-18-2-1 on the dirt) and earnings of $9,999,815, then a record for a North American runner. He was once again named Horse of the Year and champion older male for 1996.

Cigar was inducted into the Hall of Fame in 2002, his first year of eligibility.

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Other notable American win streaks include:

Hallowed Dreams

This Louisiana-bred filly also claimed 16 consecutive races, but isn't considered in the same class as those listed above because her wins came exclusively against state-restricted competition within her home state. Hallowed Dreams began her career with a maiden win on May 20, 1999 and racked up 16 straight wins from there during her two and three year old campaigns, mostly in Louisiana-bred stakes against fillies - although she did beat the boys in the D.S. "Shine Young Memorial Futurity in 1999. She scored her 16th straight victory with a win in the Tellike Handicap on June 3, 2000 at Evangeline. But she finished third in the Fantasia Stakes on June 25 to end her streak. She would retire in 2002 with a record of 30-25-1-3 and earnings of $740,144.

Peppers Pride

This mare officially holds the record for the longest American winning streak, retiring unbeaten in 19 starts. However, much like Hallowed Dreams, Peppers Pride raced only against other New Mexico-bred females in sprints within her home state. The mare made her debut on July 16, 2005, winning at Ruidoso by four and a half lengths. She immediately moved up to stakes company, finishing her 2-year-old campaign with wins in the Rio Grande Senorita Futurity and the New Mexico Cup Juvenile Fillies. She won the first start of her 3-year old campaign in January but was then laid up until October, when she returned to win her final three starts of the season. She went a perfect 7-for-7 as a 4-year-old, concluding with a win in the New Mexico State Racing Commission Handicap, to push her career mark to 14-for-14. In 2008, Peppers Pride began the year with wins in the Sydney Valenti Handicap and the Russell and Hellen Foutz Distaff Handicap, then notched her 17th straight win in an allowance/optional claiming event at Zia Park on Oct. 4, 2008. She won the New Mexico Cup Fillies and Mares Stakes that November. Peppers Pride then concluded her career with another victory in the New Mexico State Racing Commission on Dec. 14, 2008, winning by nearly six lengths under highweight of 126 pounds, giving between seven and thirteen pounds to her rivals. She retired with a perfect 19-for-19 mark and earnings of $1,066,085.

Colin

Colin was an unbeaten champion early in the twentieth century, when horses are often asked to carry weights higher than they are today and run at farther distances. His unbeaten career occurred at distances from five furlongs to a mile and three eighths, and he was asked to tote 129 pounds on multiple occasions - including twice as a 2-year-old. Colin began his career in 1907, breaking his maiden, winning the National Stallion Stakes and taking the Eclipse Stakes, all at Belmont in a span from May 29 to June 5. He won the Great Trial Stakes and the Brighton Junior before coming to Saratoga to take the Saratoga Special on August 10, then the Grand Union Hotel Stakes four days later. He finished the campaign with wins in the Futurity, Flatbush, Produce, Matron and Champagne. Colin didn't start in 1908 until the Withers Stakes in late May, but he won that, and then the Belmont a week later, defeating Preakness winner Fair Play both times. He then closed out his career with a win that June in the Tidal Stakes, finishing with a perfect 15-for-15 record and earnings of $181,610. The biggest purse he raced for was $26,640 in the Futurity.

Personal Ensign

The horse to whom Zenyatta is most often compared, Personal Ensign, regarded as one of the greatest racemares in American history, closed out her career unbeaten. Personal Ensign won her maiden by 12 lengths on Sept. 28, 1986 at Belmont, then won the Grade I Frizette by a head in her very next start. But the filly fractured her left rear pastern in a workout, ending her season and, as some thought, her racing career. But trainer Shug McGaughey was able to bring the filly back, and she returned as a 3-year-old in fall 1987 to win two allowance races, then the Grade II Rare Perfume and the Grade I Beldame, all at Belmont, making her 6-for-6 lifetime. Personal Ensign's crowning accomplishments took place during her 4-year-old season in 1988. She won back-to-back Grade Is at Belmont in the Shuvee and Hempstead, then won the Molly Pitcher at Monmouth, her first race outside of New York, by eight lengths. Personal Ensign returned to New York to beat males Gulch and King's Swan in the Whitney at Saratoga. She beat Kentucky Derby winner Winning Colors by 3/4 of a length in the Maskette, then won the Beldame for a second straight year. Personal Ensign would conclude her career in the Breeders' Cup Distaff on Nov. 5 at Churchill Downs, against the likes of Winning Colors and Kentucky Oaks winner and multiple Grade I-winner Goodbye Halo. Personal Ensign trailed the field early and struggled throughout with the muddy, sticky track, while Winning Colors loped along on an easy lead over the track she had won the Kentucky Derby on. Personal Ensign made her move rounding the far turn. In midstretch, she still appeared hopelessly beaten with Goodbye Halo and Winning Colors to catch. She gradually wore down Goodbye Halo, then nailed Winning Colors in the final jump for a stirring victory. Personal Ensign retired 13-for-13 with earnings of $1,679,880.