The structural component compositions of thirty nine non-commercial Pacific Northwest grasses were analyzed in order to develop a database of the grasses that may have application in bioconversion processes. The samples were chosen based on near infrared reflectance data that suggested this group of grasses, collectively, was representative of the broad range of compositions that are likely to be encountered due to genotypic and phenotypic variability. Solvent-extracted samples were prepared by extracting the native grass sequentially with water and then 95% ethanol. Each of the grasses residues was analyzed for glycans, acid-insoluble lignin, acid soluble lignin, and ash.  Total glycans ranged from a low of 32% to a high of 50%. Glucan was the major glycan component, typically in the range of 60% of total glycan. Xylan represented about one-third of total glycans while arabinan represented 1.0% to 3.3%. Total glycans tended to increase from the younger stage to the more mature stage. While the amount of glycans varied between species, the ratio of glucan, xylan, and arabinan (12: 7: 1) remained relatively constant.  Acid-insoluble lignin ranged from 6.38% to 14.58%, while the acid-soluble lignin ranged from 1.57% to 4.35%. The acid-insoluble lignin of seed mature, flower, boot, and vegetative stages were 12.38%, 11.65%, 9.39%, and 8.10%, respectively. The acid-soluble lignin of seed mature, flower, boot, and vegetative stages were 2.03%, 2.61%, 3.02%, and 3.46%, respectively. Extractives represented 20.29% to 41.55% of the oven-dry grasses.