Depends on where you do it and how you do it. If you register a business online, through say the Division of Corporations in your home state, it will usually be registered within the first 24 to 48 hours. Of course, you have to file all of the appropriate forms, paperwork, etc...such as your articles of incorporation, but this is usually part of the registration process. If you fill out the forms and send them in via mail, then you have to deal with all the lazy government people that sit around all day who will never process your paperwork, which will obviously take much longer.