Is it illegal to take things out of a public dumpster?

I’m working next to a furniture store. They have thrown a brand new, still-in-the-plastic queen size mattress in the dumpster. I can’t bear it! I don’t need it, but somebody could sure use it. It seems like such a horrible waste. Have you seen what mattresses go for? Hundreds of dollars!

I’ve taken lots of stuff out of dumpsters, but a mattress would be hard to hide until you were removed from the scene…but is it even illegal to take it?