This new study of the Gauss/Matuyama transition from Searles Lake, California conjoined with other records from the western United States, provides interesting insights into the structure of the reversing magnetic field. The present study employs improved measurement and data reduction techniques, multiple parallel strings of samples, and a finer sampling interval than was used in the original study by Liddicoat <1982>. Particularly crucial to this investigation was the use of overprint directions to reconstruct declinations, required because the core was rotary drilled. The results of this technique were corroborated by employing an independent method that uses anisotropy of magnetic susceptibility to resolve a sediment fabric: the fabric facilitated the alignment of core segments. The new record reveals that the main swing of the transition occurs over a significantly shorter time span than was found in the original study. In addition, it brings out several small scale variations that were absent in the old record, some of which take the form of relatively rapid jumps in direction that punctuate more steadily varying changes. This alternating steady and rapid field change is similar to behavior observed in volcanic records, which argues that such behavior is not merely an artifact of episodic volcanism. The Searles Lake record is strongly nonzonal and is defined in the Northern Hemisphere by a swath of virtual geomagnetic poles (VGPs) stretching from Northern Eurasia to west Africa and to the northwest Pacific. Glenet al. <1994> showed that a collection (spanning >15 Myr) of western North American transition and excursion records displays this same pattern, indicating that the VGP swath is a persistent feature of the transitional field. In addition, the compilation reveals that the swath extends into the Southern Hemisphere, outlining a region marked by an absence of poles that is centered on the Indian Ocean. The fact that this pattern is offset from a similar one seen in global compilations suggests that the persistent fields have a significant nondipolar component. Seven additional records are now available, making the western North America data set perhaps the finest regional set of high-resolution records consisting of both igneous and sedimentary records. The new records, which provide an important test of the existence of the VGP pattern, strongly support the findings that reveal the presence of persistent, long-term (>15 Myr) nondipolar transitional fields. ¿ 1999 American Geophysical Union