A number of crystalline forms of N-(2-((6-(3-(2,6-dichloro-3,5-dimethoxyphenyl)-1-methylureido)pyrimidin-4-yl)amino)-5-(4-ethylpiperazin-1-yl)phenyl)acrylamide are provided. These include a crystalline free base form, a crystalline monohydrochloride salt form, a crystalline dihydrochloride salt form, and a crystalline ethanesulfonate salt form. Methods of making and using crystalline compounds are also provided.