This data publication contains the results of field work in masticated materials of mixed-conifer forests in 14 study locations. Mixed-conifer masticated materials were investigated in four states of the western U.S., including Idaho, Colorado, New Mexico, and South Dakota. The data were collected from 2012 through 2016 as part of the MASTIDON project, which was a four-year research project to characterize how burning properties of masticated material are affected when different cutting machines are used to treat the forests and when masticated particles are left on the ground for multiple years to decompose. The project was funded by the Joint Fire Sciences Program (JFSP) and RMRS between 2013 and 2016. The masticated particles within this project were created by four different machines, including a vertical rotating head, horizontal drum, chipper, and mower. They had been decomposing in situ in wet and dry areas of the mixed-conifer forests since their initial treatment. This publication gives GPS locations and laser elevation data for each field site and the GPS locations where depth measurements were taken within each macroplot. It gives depths for each of the five fuel layers distinguished within the masticated materials at two scales. The first scale is at three-meter intervals along each of six transect lines. The second scale is within each microplot and quarter plot where samples were taken from the quarter plots for further lab work. The data also contain estimates of vegetation cover and height at each of the depth-measurement locations. [This data product is archived in the USFS Research Data Archive, number RDS-2017-0033.]