Planning, for the most part, is an interesting field because the major is primarily a masters degree field. There are a handful of universities that offer planning as a bachelor's degree, but at most places the degree is started at the master's level (maybe ten percent of the schools that offer a MURP have bachelor's programs, probably 15 programs in the country). I took a drafting class my junior year of high school, where second semester we did architectural drawing, yet when I doodled I drew a row of houses rather than floor plans - if I knew what Urban Planning was I would have majored in it. If I knew then what I know now, I would have been an undergrad major in Planning at Illinois, and then gone on to a joint JD/MURP. Instead I was a PreLaw/PoliSci major at Illinois, and got my JD. My specialty as an attorney is municipal law, planning, zoning, and subdivisions, and I have spent many years serving on Planning Commissions - I even worked as a Planner for a municipality.
Since you want to get a masters in planning, you have many options. You could find a school, such as Illinois, that offers planning as an undergraduate degree. But the key question might be: What is drawing you to planning? If the politics and policy interests you, polisci might be the right major for you. If the integration of architecture into a neighborhood interests you, perhaps architecture is the major. Some people get into the infrastructure of planning, like transportation and public services; they might major in civil engineering, and look to plan roads and sewer/water systems. If you are into open spaces and designs, perhaps landscape architecture is your major. Maybe if you want to be a real estate developer, you might major in Business or Finance to prepare for the business / private side of the planning field.
These different options all tie into some of the variations of masters programs which some universities offer: joint MURP and Civil Engineering, or Architecture, or Landscape Architecture, or Public Administration, or Law, or even Health Care Administration.
The American Planning Association has a book setting out all of the programs in Urban Planning in the US and Canada. You probably can find it on the APA website.