A single first-class stamp is sufficient postage for any domestic letter sent via the United States Postal Service. Therefore, only one first-class stamp is needed to send an envelop from Minnesota to California.
A standard envelope that weighs less than 13 ounces needs a first-class stamp, which costs 49 cents as of 2014. Large envelopes and parcels require additional postage. The envelop must meet the dimension requirements set by the U.S. Postal code. Senders also have a myriad of additional services available to them for first-class letters, including tracking, proof of delivery and insurance. These services need to be purchased directly from a postal agent at a local postal facility, and they carry an additional fee.