1.18-inch-thick band of sedimentary rock that serves as a snapshot of that tumultuous time, Stanley reports.

“The information contained in that thin sediment band illustrates the key feature of national natural landmarks as significant natural areas recognized for their irreplaceable features,” National Park Service Director Jonathan Jarvis says in a statement. “They teach us extraordinary lessons about the world around us. The National Park Service partners with landmark owners in support of their voluntary conservation of these important areas, another important feature of the program.”

The West Bijou Site is currently managed by the Plains Conservation Center, which has long been dedicated to the study and protection of Colorado’s plains and grasslands. The group purchased the site in the 1990s in order to offset the loss of a parcel of1990 and February 1992, the survey used a stratified, multistage probability sample of persons aged 15 to 54 years in the noninstitutionalized civilian population. The data were released for public use in 1998. The study design allowed for estimation of the national prevalence of mental illness as defined by the Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised (DSM-III-R).16

The NCS surveyed 8098 persons. Questions regarding tobacco use were asked of the 4411 respondents interviewed during the latter half of the survey (1991-1992). Specially trained staff from the Survey Research Center at the University of Michigan administered a modified version of the Composite International Diagnostic Interview (CIDI).17 The CIDI is a well-validated, structured diagnostic interview based on the Diagnostic Interview Schedule (DIS), which was used in the