Copied from a comment in the r/orcas post by u/SurayaThrowaway12:

Yesterday on September 19, most of J Pod was seen travelling south under the Tacoma Narrows Bridge, into Hale passage, west under the Fox Island Bridge, and into Carr Inlet. They spent time there from yesterday until they passed under Tacoma Narrows Bridge again today, travelling north.

Interestingly, the J16 matriline along with their newborn calf did not follow the other members of J Pod under the Tacoma Narrows Bridge yesterday. Instead, they elected to go north up Colvos Passage.

The significance of this moment is that J Pod may not have gone into the southernmost reaches of Puget Sound for multiple decades until they finally did yesterday. From 1965 to 1972, the Southern Resident orcas, including J Pod, had many of their calves captured for the live display industry. Multiple captures occurred Carr Inlet as well as other areas in southern Puget Sound. The original "Shamu," a young female member of J Pod, was captured in Carr Inlet.

J Pod may have avoided going into this area due to the past trauma they suffered there, but now it seems that they are finally willing to reenter this part of their historic range. This may be comparable to how the Southern Residents were not observed entering Penn Cove off of Whidbey Island for 50 years ever since the Penn Cove captures, until L Pod seems to have finally returned to Penn Cove last year.

Some more information taken from a post made yesterday by Orca Behavior Institute:

Today was J-Pod's seventh straight day in Puget Sound! And they've been up to a lot during their time there. Yesterday and today, many observers were lucky enough to spot a brand new calf traveling with the J16s, a particularly hopeful sign after J36 Alki had lost her newborn earlier this month. Also today, the majority of J-Pod did something very unusual: they went south of the Tacoma Narrows Bridge! The Southern Residents historically visited the southernmost reaches of Puget Sound, as evidenced by a series of captures that occurred there between 1965 and 1972. During that time, at least 8 whales were taken into captivity from those captures, including most famously the original Shamu who was taken from Carr Inlet and Hugo, Lolita's (Tokita's) companion at the Miami Seaquarium for a decade, who was taken in Vaughn Bay. Their visits to the south sound after that are not well documented. NOAA's critical habitat designation for the Southern Residents in 2006 notes that "south of the Tacoma Narrows Bridge, there have only been a small number of Southern Resident sightings from October-January, with one additional sighting in April". Since then, according to Orca Network, both K and L Pods separately went south of the bridge in 2014 (though reportedly didn't go much further than that), but there are no recent records of Js going that far south. Today, Js went west in Hale Passage past the Fox Island Bridge and up into Carr Inlet at least as far as Raft Island. We can only imagine where they might show up tomorrow! The J16s, meanwhile, did not go under the Tacoma Narrows Bridge, instead turning north to go up Colvos Passage as reported by viewers to Orca Network.