We present experimental measurements of the density, speed of sound, and vapor pressure of trans-l-chloro-3,3,3-trifluoropropene, which is also known as R1233zd(E). Densities were measured over the temperature range from (215 to 444) K, with pressures from (0.3 to 24.1) MPa. Sound speed data were measured at temperatures between (290 and 420) K, with pressures from (0.07 to 2.1) MPa. Vapor pressures span the temperature range from (280 to 438) K. The experimental data cover the saturation curve, the vapor and liquid phases, and also the vicinity of the critical point. Densities and vapor pressures were measured in a two-sinker densimeter with a magnetic suspension coupling. Sound speed data were measured with a spherical acoustic resonator. An equation of state written in terms of the Helmholtz energy was developed; it represents the present experimental data with relative root-mean-square deviations of 0.020 % for densities, 0.223 % for vapor pressures, and 0.131 % for speeds of sound.