We present results from an atmospheric retrieval analysis of Gl 229B using the Brewster retrieval code. We find the best fit model to be cloud-free, consistent with the T dwarf retrieval work of Line+ 2015ApJ...807..183L & 2017ApJ...848...83L; Zalesky+ 2022ApJ...936...44Z and Gonzales+ 2020ApJ...905...46G. Fundamental parameters (mass, radius, log(L_Bol_/L_Sun_), log(g)) determined from our model agree within 1{sigma} to SED-derived values, except for Teff where our retrieved Teff is approximately 100K cooler than the evolutionary model-based SED value. We find a retrieved mass of 50_-9_^+12^M_Jup_, however, we also find that the observables of Gl229B can be explained by a cloud-free model with a prior on mass at the dynamical value, 70M_Jup_. We are able to constrain abundances for H_2_O, CO, CH_4_, NH_3_, Na and K and find a supersolar C/O ratio as compared to its primary, Gl 229A. We report an overall subsolar metallicity due to atmospheric oxygen depletion, but find a solar [C/H], which matches that of the primary. We find that this work contributes to a growing trend in retrieval-based studies, particularly for brown dwarfs, toward supersolar C/O ratios and discuss the implications of this result on formation mechanisms and internal physical processes, as well as model biases.