Summary: We first extend the Peierls algebra of gauge-invariant functions from the space \(\mathcal S\) of classical solutions to the space \(\mathcal H\) of histories used in path integration and some studies of decoherence. We then show that it may be generalized in a number of ways to act on gauge-dependent functions on \(\mathcal H\). These generalizations (referred to as class I) depend on the choice of an “invariance-breaking term”, which must be chosen carefully so that the gauge-dependent algebra is a Lie-algebra. Another class of invariance-breaking terms is also found that leads to an algebra of gauge-dependent functions, but only on the space \(\mathcal S\) of solutions. By the proper choice of invariance-breaking term, we can construct a generalized Peierls algebra that agrees with any gauge- dependent algebra constructed through canonical or gauge-fixing methods, as well as Feynman and Landau “gauge”. Thus, generalized Peierls algebras present a unified description of these techniques. We study the properties of generalized Peierls algebras and their pullbacks to spaces of partial solutions and find that they may possess constraints similar to the canonical case. Such constraints are always first class, and quantization may proceed accordingly.