We report the synthesis of high molecular weight (MW), high crystallinity (X(c)) poly(L-lactic acid) (PLLA), with improved thermal stability, by solid state polymerization (SSP) of low MW PLLA prepolymer, pre-PLLA. SSP enabled pre-PLLA is synthesized by ring opening polymerization (ROP) of L-lactide using a ternary catalyst complex of L-lactide, stannous octoate, and L-lactic acid oligomer (OLLA). We demonstrate that this ROP, although a chain-growth reaction, yields pre-PLLA with end-groups, which enable step growth SSP. MW increases similar to 9 fold, with X(c) reaching beyond 90%, during the SSP process. Such high values of crystallinity could be due to the synchronization of the crystallization rate with that of the slower and longer lasting step-growth SSP. Nuclear magnetic resonance spectroscopy confirms that SSP is indeed a step-growth reaction. In comparison, Zn(OLLA)(2) only couples two pre-PLLA chains during SSP. In addition, the radial spherulite growth rate has been quantified with annealing time of SSP synthesized PLLA. POLYM. ENG. SCI., 51:2078-2084, 2011. (C) 2011 Society of Plastics Engineers