On June 2, 1924, the Massachusetts General Court passed legislation authorizing the state Department of Public Utilities (DPU) to construct an infill station at Charles Street. Following a 1924 study by the Boston Transit Department (BTD), the DPU delegated the project to the BTD on January 12, 1925. That study also considered an extension of the East Boston Tunnel to Charles Street to provide a transfer between the lines. The project stalled in 1926 as the $600,000 appropriated by the legislature was only sufficient for four-car platforms, while the BERy insisted on six-car platforms at a cost of $850,000 to accommodate its future plans.