The peer-to-peer nature of a wireless sensor network presents the opportunity for accurate and low-configuration sensor location estimation. Range measurements are made between pairs of sensors, regardless of their a priori coordinate knowledge. This paper quantifies via the Cramer-Rao bound (CRB) variance limits on location estimators which use measured time-of-arrival (TOA) or received signal strength (RSS). An extensive campaign measures TOA and RSS in a 44-device multipoint-to-multipoint indoor network for input into maximum-likelihood estimators (MLE) of location. RMS location errors of 1.2 and 2.2 m are demonstrated using TOA and RSS, respectively.