Hi all - just noticed this today - after having traveled the southwest (So. Cal & AZ) the better part of 6 weeks ... not sure if this is new or not, growing or not, (although the same size appears on the other side) ..
(image should be attached (apologies for its rotated view (you can click image to see up close) - but there's also a PDF of the image with a yellow circle encompassing the crack - )
The crack is in the metal right next to the weld. That is the weakest point in a welded structure, because the metal there has been heated and cooled, but has not had reinforcing metal added, as is done in the weld bead itself.
Sometimes a poorly done weld will look like there's a crack where the weld did not penetrate properly. That's not the case here. That's a good, professional-looking weld with a stress crack next to it, in my opinion.
Rust inside the crack says it's been there for a while.
Replace it. It's definitely not going to get better.
Let's not panic. Yep, it's definitely cracked. But it has been cracked for quite a while— no telling how long— judging from the corrosion, and there is no evidence that the crack has lengthened or spread recently since it all appears to be weathered the same. Which means the problem isn't getting worse despite you still using the hitch.
I definitely recommend replacement in the near future, but you still have enough good metal on your hitch to be able to use it long enough to get home. But just as there's no telling how long the crack has been there, there's no telling how long it will be before it gets worse, if ever. Just make sure you inspect it every day of towing, and if the crack does visibly grow (you'll be able to tell from shiny metal on the edges of the crack where it has lengthened) THEN park the trailer until you can get the hitch replaced.
Engineering: Finding complex solutions to simple problems you didn't even know you had.