What Spider species live in and around the North Jersey area that builds nest out of mud?

I was cleaning my room one day and I discovered a nest made out of mud on the top right corner of my window. The window being slightly cracked open. I knew what a wasp's nest looks like and yet perhaps I thought this was some other flying insect's nest. In my attempt to cover it with a towel to scoop it and throw it out I broke a piece of it and two dead spiders fell out. I was in total shock. I've never seen or heard of any spiders in the North Jersey Area building a nest out of mud that looked like a small mound. I wish I could describe what the designs on the back of the spiders looked like but I was to busy eventually breaking the mound and quickly throwing it away out the window. I did try to look for it outside but to no avail. The nest was super hard. In my first attempt I wasnt able to break it. I believe it completely dried and thus the spiders couldnt get out and died inside. However, I couldnt verify if others survived inside.