Definitely not the first, surprisingly hard to find clear data about the endpoints of the ties themselves but this random court document has a fairly clear diag

Definitely not the first, surprisingly hard to find clear data about the endpoints of the ties themselves but this random court document has a fairly clear diagram on page 3: https://www.nrg.com/assets/documents/energy-policy/ferc_workshop_on_interregional_transfer_capability_requirements_120622.pdf https://www.nrg.com/assets/documents/energy-policy/ferc_work... ERCOT also reports flows for the four existing DC ties: https://www.ercot.com/gridmktinfo/dashboards/dctieflows https://www.ercot.com/gridmktinfo/dashboards/dctieflows With that said the biggest tie is like half a GW, so my guess is that they used the term "power markets"" rather than "power grids" because the current links don't really function as a way to transfer bulk power between markets, even if the Texas grid is technically already connected outwards. Like in an emergency they can import a miniscule amount of power, but nobody's going to be seriously arb'ing power with the existing ties.