We present Hubble Space Telescope (HST ) Space Telescope Imaging Spectrograph (STIS) G140M spectra of 15 extragalactic targets, which we combine with GHRS/G160M data to examine the statistical properties of the low-z Ly forest. With STIS, we detect 109 Ly absorbers at significance level (SL) of !4 over 0:002 < z < 0:069, with a total redshift path length Áz ¼ 0:770. Our combined sample consists of 187 Ly absorbers with SL ! 4 over Áz ¼ 1:157. We evaluate the physical properties of these Ly absorbers and compare them to their high-z counterparts. Using two different models for Ly forest absorbers, we determine that the warm, photoionized intergalactic medium contains 29% AE 4% of the total baryon inventory at z ¼ 0 (assuming J 0 ¼ 1:3 Â 10 À23 ergs cm À2 s À1 Hz À1 sr À1 ). We derive the distribution in column density, N À1:65AE0:07 H i for 12:5 log N H i (cm À2 ) ½ 14:5, breaking to a flatter slope above log N H i ½ % 14:5. As with the high equivalent width (W > 240 m8) absorbers, the number density of low-W absorbers at z ¼ 0 is well above the extrapolation of dN =dz from z > 2. However, log (dN =dz) z¼0 ½ ¼1:40 AE 0:08 for W > 240 m8 is 25% below the value obtained by the HST QSO Key Project, a difference that may arise from line blending. The slowing of the number density evolution of high-W Ly clouds is not as great as previously measured, and the break to slower evolution may occur later than previously suggested (z $ 1:0 rather than 1.6). We find a 7.2 excess in the two-point correlation function (TPCF) of Ly absorbers for velocity separations Áv 260 km s À1 , which is exclusively due to the higher column density clouds. From our previous result that higher column density Ly clouds cluster more strongly with galaxies, this TPCF suggests a physical difference between the higher and lower column density clouds in our sample. The systematic error produced by cosmic variance on these results increases the total errors on derived quantities by $ ffiffi ffi 2 p .