ALMS was bought out by IMSA (in 2013?). P1 category is gone from the combined series.
It's a bit worse than that. ALMS was actually bought by "NASCAR," and combined with the Daytona Prototype series known as the Rolex Series. IMSA was "revived" as the sanctioning body. They bought pretty much everything Panoz had owned/created, including Road Atlanta. P1 was eliminated; P2 was combined with the Daytona Prototypes; PC (Prototype Challenge spec class), GTLM (LeMans), and GTD (Daytona) were continued. Part of the problem is the performance difference between the P2 and DP cars - the attempts to equalize the two have not been very successful. Having the two GT classes, with considerably different performance, is confusing, as is having a PC class of cars that look like the P2 cars. On top of all that, everyone is required to use Continental tires, except GTLM - they can use whatever they want, since those cars were developed using other brands of tires, particularly Michelin.
I was a big fan of the ALMS - I liked the cars. I've never been a fan of the DP cars - ugly. But, it's the only sports car racing series we have that's on TV, or FoxSports!/FoxSports2/IMSA.com/FoxSports1. We used to have a great channel in Speed, but Fox and NASCAR screwed that.
Sigh.
Mike