Tracking USPS

Does anyone know the url to pass a tracking no. to USPS and have it display the tracking info?

For example the one for UPS is wwwapps.ups.com/tracking/tracking.cgi?tracknum=%1 where %1 is replaced with the tracking No.

I have an answer:

http://trkcnfrm1.smi.usps.com/PTSInternetWeb/InterLabelInquiry.do?origTrackNum=%1

where %1 is the tracking no.