historically, the number of structures in the csd has grown at an approximately exponential rate passing the 25,000 structures milestone in 1977, the 50,000 structures milestone in 1983, the 125,000 structures milestone in 1992, the 250,000 structures milestone in 2001, the 500,000 structures milestone in 2009, and the 1,000,000 structures milestone on june 8, 2019. the one millionth structure added to csd is the crystal structure of 1-(7,9-diacetyl-11-methyl-6h-azepino[1,2-a]indol-6-yl)propan-2-one.