Myoglobin was the first protein to have its three-dimensional structure determined by X-ray crystallography: 
Kendrew JC, Bodo G, Dintzis HM, Parrish RG, Wyckoff H, Phillips DC (1958) A Three-Dimensional Model of the Myoglobin Molecule Obtained by X-Ray Analysis. Nature 181(4610): 662-6. 
For this achievement, John Kendrew shared the 1962 Nobel Prize in chemistry with Max Perutz. 
http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1962/ 
"Myoglobin is an iron- and oxygen-binding protein found in the muscle tissue of vertebrates in general and in almost all mammals." 
--http://en.wikipedia.org/wiki/Myoglobin 
One STL file contains a representation of the protein in cartoon form with residues binding the heme group represented as spheres (in green in the images). A separate STL file contains the heme group itself (in red in the images). Model based on the Protein Data Bank entry 1MBN: 
--http://www.pdb.org/pdb/explore/explore.do?pdbId=1mbn 
Model created using VMD: 
http://www.ks.uiuc.edu/Research/vmd/