The first US Routes in Connecticut, US 1, 5, 6, and 7, were laid out in 1926. They took over from the existing New England Interstate route system. In 1935, Routes 44 and 202 were added, to encourage tourism.
There have been several "A" routes in the past, including many for US 1, 5, and 6; in 1941, for example, three US 6A's overlapped each other on US 6. However, now all of them are gone except for US 1A, in Stonington.
For details, see: