It seems to be a very big year for Pink Lady Slipper blooming in my neighborhood. One in my yard blooms every year. Most years it is the only one that does. This year several more (on my less than a acre, less than half of which is woods they grow in).
Walking through, they are very hard to spot despite the pink color, because they tend to grow better hidden under other plants. If you zoom into this photo, it is not too hard to find four blooming. Before I went to get my camera, I found five here that I thought I could get into one shot. When I came back with the camera, I tried hard but could only find four there:
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Closeups of Those four are:
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Nearby, out in the open, the one that blooms every year:
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On the other side of the path, I had found four a few days ago, but only found two today (I guess I'm pretty bad at spotting these):
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I decided to get photos because I was talking to someone who walks around this neighborhood a lot and thought these were rare and endangered and was commenting that she saw several of them today (not the ones in my yard). I explained that they aren't actually rare here or endangered, but in any one year most of them don't bloom, so you tend not to spot them. I also saw far more non blo0ming ones this year than typical. Maybe there are more. More likely, I was just looking more closely.

Either that or maybe something nipped the flower.
Some is better then none.

New Jersey is having a great Cyp acaule year!! Visiting the old stands, we found lots in bloom and many juveniles.
Now North East Pennsylvania where we have a place, is not doing that great this year, the second year in a row we saw lots of juveniles and very few in bloom. But then it was a very long cold spell in that region and all wildflowers were really slow to come up.
Regarding the rare /endangered part - I have only shared the location of our stands with very few trusted friends. Many people don't realize that removing them from their specific habitat spells a sure death to the plant and might be tempted to dig them up.
And no, they are not that rare, if you know where to look, but I still consider them protected!

Cypripedium acaule are not rare or endangered as far as I know but in a great many cases, they are protected by both State and Federal Law.
Most flora and fauna are.

jsf67 -- Thank you for posting those photos. I appreciate the "whole habitat" shots because they show the plants preferred conditions & neighbors.

Oh, I should have added secrecy. Once found a lot of people who realize what they have keep 'mum' about the slippers.

I just sent my son still living on Long Island to check on a large population that we knew about.
He reports that they have spread out like an amoeba. Flowers numbered close to 1,500 he reports. Some dense pockets had over a hundred plants in a living room sized area. There are indications they said of perhaps 5,000 seedlings coming. Small, non blooming plants were everywhere!!
This was wonderful news since I first saw these guys back in May of 1971! That's 51 years if my math is right. At that point they were tightly grouped and easier to survey. Nature does win some after all!

Edited to add, these are a deep Rose red color form, much darker then most images I have seen.
One good friend of mine back in the late 70's early 80's, turned slides into maybe a 30" wide by 12" photograph, matted and framed, that they hung in their living room. I wonder if that image survives.

I know that AOS renowned watercolor artist, Angela Mirro, visited this group often and one year made a Show Poster for the Greater New York Orchid Society Show back 40 years ago. It was stunning!! I lost my copy somehow in one of my moves.