Abstract　 　　
　 The baryon acoustic oscillations (BAO) are an excellent standard ruler that can be used to infer a distance-redshift relation, a powerful tool for constraining cosmological parameters. Most past BAO analyses have focussed on using information in the isotropic BAO signal, however, this returns a degenerate measure of the angular diameter distance and the Hubble parameter. Analyzing the anisotropic BAO information, i.e. the full 2D clustering distribution of galaxies, allows us to simultaneously measure D_A(z) and H(z). This allows us to directly probe the expansion history of the Universe through H(z). In this talk I will outline the basics of BAO measurements and present the theory behind the anisotropic BAO analysis. I will then show results from SDSS DR7 and DR9.