Which Apple tablet app followed Pinterest's iPhone app in 2011?

Pinterest’s iPad app followed its iPhone app in 2011. The iPhone app launched in early March 2011 and produced more downloads than Pinterest expected, helping expose the service to a much larger mobile audience.

The iPad version was part of Pinterest’s early expansion beyond the desktop website. It was followed by Pinterest Mobile, a mobile-web version intended for people who did not use an iPhone. This sequence reflects the Apple-centered mobile market of the period: Pinterest first optimized for the iPhone, then adapted its visual pinboards to the iPad’s larger screen.

The answer is not “iPod app.” An iPod touch could run some iPhone-compatible software, but the historical account specifically identifies an iPad app. Pinterest later expanded to Android and other platforms as its audience grew.