We reconstruct the rare decays B+→K+μ +μ-, B0→K*(892)0μ +μ-, and Bs0→(1020)μ+μ - in a data sample corresponding to 4.4fb-1 collected in pp̄ collisions at √s=1.96TeV by the CDF II detector at the Tevatron Collider. Using 121±16 B+→K+μ +μ- and 101±12 B0→K*0μ +μ- decays we report the branching ratios. In addition, we report the differential branching ratio and the muon forward-backward asymmetry in the B+ and B0 decay modes, and the K*0 longitudinal polarization fraction in the B0 decay mode with respect to the squared dimuon mass. These are consistent with the predictions, and most recent determinations from other experiments and of comparable accuracy. We also report the first observation of the Bs0→μ+μ- decay and measure its branching ratio BR(Bs0→μ+μ-)= [1.44±0.33±0.46]×10-6 using 27±6 signal events. This is currently the most rare Bs0 decay observed. © 2011 American Physical Society.