The EXCELS! Project of the Anchorage School District (Alaska) was initiated in 1994 through a grant from the U.S. Department of Education to demonstrate the development of a kindergarten through sixth grade instructional program reflecting state and national standards in History, Civics, Geography, and English. More than 1,200 Anchorage teachers and librarians participated in the EXCELS! training and curriculum development activities. A multifacted assessment was later undertaken under the direction of the Anchorage School District Assessment and Evaluation Department. This paper reports on a particular performance-based assessment for grade 4, the Jamestown Assessment Unit. This unique integrated unit focused on U.S. colonial history and the settlement of Jamestown (Virginia). Over the 2 years of development, more than 70 people contributed to the final development of the Jamestown Assessment Unit. Fifteen teachers and more than 400 students field tested elements of the assessment and scoring procedures. All fourth grade teachers know that they may be called on to offer this unit as part of the Anchorage Assessment Program. In spring 1997, 412 students participated in the Jamestown Assessment Unit. Statistical analyses of the data from 368 students show that student work generated as part of instruction may be used for a standardized assessment of student and program performance relative to local, state, and national standards. The Jamestown Unit is an operational definition of an authentic assessment, scorable by both trained raters and teachers. (Contains 22 references.) (SLD)