Nearly three decades since the show first aired, the best ER episodes still thrill fans to this day. With 15 seasons that aired from 1994 to 2009, ER stood as television’s longest-running medical drama for a decade after its grand finale.Created by Michael Crichton, who wrote novels such as Jurassic Park, ER is one of the most commercially successful and critically acclaimed series in the history of television. Each season had those standout episodes that further cemented it as great television.

The cast of ER was a massive ensemble that changed over the years, including Noah Wyle, Maura Tierney, and George Clooney in his breakout role. The intensity and sometimes graphic nature of the show helped to change network television and could be seen as a precursor to the era of prestige television. The fast-paced look at the world of emergency room doctors certainly made for exciting moments and the best ER episodes from each season show why the show was so gripping.

16 Season 1 - "Love's Labor Lost"

Episode 19 of ER season 1, “Love’s Labor Lost,” is one of the most unanimously beloved installments in the history of the show. In it, viewers see Dr. Greene misdiagnosing a pregnant woman, causing the County General doctors to scramble to save her and her baby’s lives. It's an episode that masterfully allows its audience to sympathize with the patients as well as the doctors as everything that can go wrong does go wrong. During that awards season, “Love’s Labor Lost” won five Emmys. It is safe to say that this episode solidified ER’s place on TV, turning it into a primetime ratings juggernaut that also garnered wide critical acclaim.

15 Season 2 - "Hell And High Water"

George Clooney became a star on ER, helping to launch his movie career. Dr. Doug Ross (Clooney) was certainly one of the standout characters from the very beginning of ER, but fans might argue that season 2’s “Hell and High Water” episode really solidified his importance on the series. What’s more, this episode definitively showcased the types of stories that ER could tell, many of which did not have to take place inside a hospital. Doug spends the bulk of the episode on his own trying to rescue a boy stuck in a storm drain, and it was a truly thrilling and action-packed installment.

14 Season 3 - "Night Shift"

Season 3’s “Night Shift” shows the County General doctors facing what is an otherwise slow night at the hospital. However, that is not to say that these characters don’t deal with their fair share of conflicts that make this episode the highlight of that season. Overall, “Night Shift” places a focus on the behind-the-scenes lives of ER's doctor characters, rather than showcasing more complicated medical cases in the form of new patients. For instance, Greene is faced with a legal matter, while Carter must come to grips with the ongoing tension between Benton and Grant.

13 Season 4 - "Exodus"

This particular episode embraces a perennial trope of nearly every medical and procedural drama in history that fans never seem to stop loving: the catastrophic event. A chemical spill causes several patients to end up in County General Hospital, making “Exodus” one of the most exciting event episodes in the history of ER. During this episode, Dr. Carter takes charge of the emergency room, along with Ross, Hathaway, and Corday facing obstacles of their own. ER knows how to pull off the big grand spectacles without sacrificing the show's grounded feel and this is a perfect example of that.

12 Season 5 - "The Storm, Part 2"

In hindsight, many fans remember season 5 as George Clooney’s (Dr. Doug Ross) last year on ER. More specifically, however, the highlight of that season was the two-parter “The Storm” episode which was his last show as a series regular. It was very hard saying goodbye to Dr. Ross on ER, and “The Storm” certainly made fans cry their hearts out as they watched him make the decision to leave County General Hospital. Thankfully, George Clooney did appear as a special guest on ER twice more, in season 6 episode 21 (“Such Sweet Sorrow”) as well as in season 15 episode 19 (“Old Times”).

11 Season 6 - "All In The Family"

Saying goodbye to Dr. Lucky Knight (Kellie Martin) was one of the most challenging and memorable moments ever for ER fans. The Valentine’s Day-themed “All in the Family” episode follows the stabbing of Dr. Knight (as well as Dr. Carter) that leads to her death. Although ER clearly knew how to amp up the drama in seasons past, this was really a landmark episode for the show, which is clearly reflected by the fact that it remains one of the most acclaimed and popular episodes of the entire series.

10 Season 7 - "Rampage"

Unsurprisingly for a show titled ER, the emergency events that have widespread consequences for the hospital, as well as the characters, tend to elicit the best reactions from fans. "Rampage" is the last installment of season 7 in which a shooter endangers County General clearly made a strong impression. The episode was also particularly memorable because of Mark Greene's shocking choice to withhold medical treatment because of the threat that the gunman poses to him personally.

9 Season 8 - "On The Beach"

Season 8’s “On the Beach” marks the death of Dr. Mark Greene (Anthony Edwards), which is an unforgettable moment in the history of the series. Throughout the episode, fans see Greene on his final days as he visits Hawaii and reconciles with his family. Although most of ER took place within the confines of County General, this was one of the rare episodes where ER had little to do with medicine and more to do with the lives of the characters that existed on the show. Mark Greene was a part of the bedrock of the series, so losing him made an impression on viewers.

8 Season 9 - "Kisangani"

“Kisangani,” the finale for ER season 9, shows Carter volunteering in Africa and treating victims of a Civil War in the Congo. During that episode, the show completely stepped out of Chicago (a rare event for the series) and focused on Carter struggling to treat patients in a country with very few resources. After Carter reunites with Kovac in Congo, the two of them find themselves in the middle of a conflict between opposing Congolese tribes. For a show that had already been around for so long, it is impressive that it was able to find new and exciting approaches to its stories like this one.

7 Season 10 - "Freefall"

There have been a number of ER doctors to die on the show but few that received as positive a response as this one. “Freefall” is remembered by many as the episode where Dr. Robert Romano (Paul McCrane) dies, which comes as the result of a helicopter crash. Although his coworkers weren't sad to see him go, fans were both elated and bummed to see County General's resident villain kick the bucket. After ten years on air, this episode proved that ER could still surprise its audience and take chances as it furthered its storytelling.

6 Season 11 - "The Show Must Go On"

Noah Wyle had an exceptionally long run on ER, so it should come as no great shock that the show did its best to give him a great sendoff. Dr. Carter’s exit from ER is marked by various surprise appearances and many moments that caused fans to worry and cry. In true ER fashion, his farewell party is paralleled by wild circumstances that the County General doctors must face. Moreover, four interns start working at the hospital, signaling that there’ll be new blood substituting Carter, bringing his character arc in the series full-circle.

5 Season 12 - "Twenty-One Guns"

There’s a shootout in the County General Hospital, and the gunmen start getting more and more anxious. To make matters worse, Kovac unintentionally puts himself in the middle of the action. The season 12 finale “Twenty-One Guns” is a riveting and gut-wrenching episode that introduced an oft-imitated storyline for medical dramas on TV: gunmen in the hospital. This was not only innovative storytelling for TV, but it also raised the stakes for ER after 12 years on the air.

4 Season 13 - "Bloodline"

The plot of season 13 premiere “Bloodline” immediately followed the season 12 finale (“Twenty-One Guns”) shootout that changed County General Hospital forever. During this episode, the doctors are trying to treat Markovic and Lockhart (who is pregnant), both of whom were injured during the shooting. All in all, the County General doctors on ER struggle to deal with the aftermath of the events that took place in the season 12 finale, making this a high-stakes and incredibly compelling episode to watch.

3 Season 14 - "The War Comes Home"

“The War Comes Home” opened season 14 of ER with a bang. Several casualties from an anti-war rally in Chicago brings many patients to County General Hospital, causing Abby, Morris, and Pratt to struggle to tend to everyone. What’s more, Gates ends up with a patient that he suspects started the explosion that set off these casualties. The first episode of ER season 14 is by far the highlight of that season, and it would go on to become the show’s second-to-last year on TV.

2 Season 15 - "And In The End"

1

No one would really argue that “And In The End…” was anything other than the highlight of season 15. After all, it was the grand finale to the longest-running medical drama on primetime TV at that point, as well as a series that really did make television history. Unsurprisingly, the show's last episode paid homage to the 300+ installments that came before it, and many fan-favorite characters and actors who had left the show years ago came back to bid farewell to County General for the last time. It was a fitting end to ER after 15 seasons.