Applied in February, took online assessments, and then had a phone interview. About 2ish months later I recieved the call I got the internship at Headquarters. The process is longer than your typical internship interview for the reasons A) it's government and B) They do extensive background checks.
But if you get the chance to do this internship, do it! If you aren't a DC native or have connection/place to stay in DC, it can be expensive, trust me, I am from the midwest. But if you are a woman (strictly for women), Thompson Hall is cheap and pays for your meals, or stay at GWU (regardless of gender). I stayed at GWU Shenkman Hall apartments, which are right next to the Foggy Bottom Metro, Georgetown (a 15 minute walk), literally right down the street is the Lincoln Memorial, and you have Whole Foods and Trader Joes in walking distance. Not to mention the life of Foggy Bottom is always something to do!
At USPS, you learn so much about everything, meet really awesome interns regardless of your personality type. The atmosphere at Headquarters can be a variety depending on what department you are in, but I geniuinely enjoyed the people I was able to work with. Not only that but the coordinator is really fantastic, attentive, and they really equip and mentor you! Don't pass this opportunity up!!