  We introduce an optical tweezer platform for assembling and individually
manipulating a two-dimensional register of nuclear spin qubits. Each nuclear
spin qubit is encoded in the ground $^{1}S_{0}$ manifold of $^{87}$Sr and is
individually manipulated by site-selective addressing beams. We observe that
spin relaxation is negligible after 5 seconds, indicating that $T_1\gg5$ s.
Furthermore, utilizing simultaneous manipulation of subsets of qubits, we
demonstrate significant phase coherence over the entire register, estimating
$T_2^\star = \left(21\pm7\right)$ s and measuring
$T_2^\text{echo}=\left(42\pm6\right)$ s.
