  We analyse the asymptotic symmetries of Maxwell theory at spatial infinity
through the Hamiltonian formalism. Precise, consistent boundary conditions are
explicitly given and shown to be invariant under asymptotic angle-dependent
$u(1)$-gauge transformations. These symmetries generically have non-vanishing
charges. The algebra of the canonical generators of this infinite-dimensional
symmetry with the Poincar\'e charges is computed. The treatment requires the
addition of surface degrees of freedom at infinity and a modification of the
standard symplectic form by surface terms. We extend the general formulation of
well-defined generators and Hamiltonian vector fields to encompass such
boundary modifications of the symplectic structure. Our study covers magnetic
monopoles.
