On April 2, there will be a mighty farewell. “ER” is coming to an end after 15 years on television. There are no original members of the cast, as series regulars and the series as a whole have weathered a serious ratings decline, but there are still some fans out there. Take a walk down the trauma center hallway — or memory lane — as we look back on some of “ER’s” milestones including departures, heartbreak, bipolar moms, returns and helicopters.

The departure/return/departure of Dr. Susan Lewis (Sherry Stringfield).

In the season three episode “Union Station,” Stringfield’s character follows her sister and niece to Phoenix. Stringfield was the first cast member to depart the hit medical drama and the first to return as more than a guest star. In season eight’s “Never Say Never,” Dr. Lewis returns to Chicago looking for a job, and it just so happens County General has an opening. Stringfield left the show again in season 12 without a farewell episode. Stringfield is reported to return again by the end of the series.

The death of Dr. Mark Greene (Anthony Edwards).

Edwards’ character battled a brain tumor for a bit and finally succumbs, but not before reuniting his fractured family and taking them to Hawaii for a family vacation. It’s there Greene dies with Israel Kamakawiwo’ole’s haunting cover of “Somewhere Over The Rainbow” as background music.

Sally Field scrubs in.

Dr. Abby Lockhart (Maura Tierney) never had it easy on “ER.” She had a deadbeat ex-husband who didn’t pay her medical school bills and experienced a violent beating by a psychotic neighbor, so why would having her mother visit be a cakewalk? Field played Maggie, Abby’s bipolar mother, for several episodes, often leaving chaos in her wake.

Helicopters!

Dr. Robert Romano (Paul McCrane) was an ass to say the least. An ass with bad luck when it comes to helicopters. First, his arm is chopped off by one in season eight, then in season 10 one falls on him while he’s standing in the ambulance bay. Yeah, he died.

The final season.

“ER’s” final season saw the addition of Angela Bassett as Dr. Cate Banfield, the departure — and brief return — of Dr. Abby Lockhart, and a whole busload of other former cast members including Paul McCrane, Laura Innes, Anthony Edwards, Noah Wyle, Sherry Stringfield, Eriq La Salle, George Clooney and Julianna Margulies.

These are just a few moments in “ER’s” history. Head to bupipedream.com and share your thoughts.