I'm not sure what you mean by 'accredited'.  All courses offered by universities are accredited by the university.  In terms of professional accreditation, there is no professional licensing body for urban design in the US, so no course will be accredited in that way.

External accreditation is important for gaining a professional qualification.  If you want to become a licensed architect, it is important to go to an accredited architecture program. Since there is no such thing as a 'licensed urban designer', this will not apply for these courses.  A lot of people looking to gain both do a joint program, so apply to an architecture school that has a MUD program and do them at the same time (this usually adds more time to the architecture degree, but less time then it would take to do both separately.

For example, I did this myself at Washington University in St. Louis and it added one semester and one summer to my architecture degree requirements in terms of time- although I also had to choose my elective classes and studios to align in some cases as well (keeping in mind this was many years ago now).

Good luck!

Thank you so much Kayla!

What you said makes sense.I had decided that I was apply to M.arch programs with a urban design concentration. But as I started consolidating my list of colleges and programs offered, I started seeing a few urban design programs accredited by NAAB! eg: the SCAD MUD program is actually accredited by NAAB. I'm not sure what this really means.I've been caught up with work, so in the next few days I will investigate this a little more.