What can be measured by an observer in our universe? I will address this question by constructing an algebra of gravitationally-dressed observables accessible to comoving observers in FLRW spacetimes that are asymptotically de Sitter in the past, describing an inflationary epoch. An essential quantized degree of freedom is the zero-mode of the inflaton, which leads to fluctuations in the effective cosmological constant during inflation and prevents the existence of a maximum entropy state in the semiclassical limit. Due to the inaccessibility of making measurements beyond our cosmological horizon, I will demonstrate that all states have non-zero von Neumann entropy corresponding to the generalized entropy of the observer's causal diamond, a fine-grained quantity that is sensitive to the initial conditions of the universe.