The original compilation of the four numbers of Volume 3 includes a "Subject Index" and "Authors' Index" (at the beginning) and a "Topical Index" (at the end). The search box on the main Oregon Historical Quarterly page offers similar functionality.
OREGON HISTORICAL SOCIETY
MARCH, 1902–DECEMBER, 1902
EDITED BY FREDERIC GEORGE YOUNG
W. H. LEEDS, STATE PRINTER