All companies have web addresses. united states post office - usps.com, united parcel service - ups.com. They should be able to give you that information. I always use priority thru the post office and I get a tracking #. Browse the site. Its a little early in the states hopefully someone will have a definate answer a little later in the day.
The best way is to get a delivery confirmation receipt. It provides you with a tracking number that you can use to track your package online (like UPS and Fedex). The only other way is to send by Express mail.