21st Century Civilian Conservation Corps Act This bill establishes and provides grants for the Civilian Conservation Corps Program and makes supplemental appropriations for various federal departments, agencies, and programs, including the Forest Service and the Bureau of Land Management. The bill removes the limitation on the amount that may be transferred to the Reforestation Trust Fund. The bill establishes the Reforest America Grant Program for land in need of active reforestation due to high intensity wildfire, pest infestation, invasive species, and drought or other extreme weather. The bill makes additional supplemental appropriations in FY2020 for various programs, including state fire assistance. It also makes supplemental payments for climate stewardship practices such as alley cropping, conservation crop rotation, critical area planning, forage and biomass planning, and multistory cropping. .