A classification is given for
S1 bundles with structure group O(2) and base space a 2-manifold with nonempty
boundary. This result is used to obtain equivariant and topological classification
theorems for closed 3-manifolds which admit a local S1 action; i.e., a decomposition
into circles and points such that each decomposition element has an invariant
neighborhood admitting an effective circle action with the elements of the
decomposition as orbits. This extends certain results of Orlik and Raymond and
corrects a theorem of Orlik, Vogt, and Zieschang.