The series was cancelled on March 14, 2012, following animal safety concerns after three horses died during production, despite having already been renewed for a second season of 10 episodes.

Creator David Milch had been thinking about making the series for 25 years, drawing on childhood memories of his father taking him to the Saratoga racetrack from age 5 or 6.

Milch always envisioned the show being set at Santa Anita Park, calling it 'the most beautiful setting for horse racing' he had seen.

The role of washed-up jockey Ronnie is played by Gary Stevens, a real-life Hall of Fame jockey who won the Kentucky Derby, Preakness Stakes and Belmont Stakes, and who had previously portrayed jockey George Woolf in the 2003 film Seabiscuit.

Production used 50 horses trained by Matt Chew at Santa Anita, with Milch noting that about 45 of them adapted well to being part of the show's 'herd'.

PETA criticized the production after two horses were injured and euthanized during filming of the pilot and the seventh episode, with the American Humane Association confirming both horses suffered severe, inoperable fractures after stumbling during racing sequences.

HBO stated that each horse was limited to three runs per day with rest periods in between as a safety precaution, and on March 13, 2012, agreed to suspend all filming involving horses following the death of a third horse.

At the time of cancellation, the second episode of season two was already in production, but the footage shot for the second season has never been publicly released.

The show's theme song is 'Splitting the Atom' by Massive Attack.