Every major regional ISO does in North America and most of the ones in the equivalent market organizations in Europe do as well. The historian data this uses was made easily publishable about 8 years or so ago and you can get quite detailed API dumps from most of them, although usually at a time-delay to meet their requirements for market protection.

Worldwide OSIsoft's PI is the outsized leader in that but there are numerous other historians with modernized REST API outputs, etc, from Canary Labs and most SCADA systems will at least include their own discount version built on top of Postgres or something. The more dedicated ones use time-series databases versus relational ones but with modern storage and processing that isn't as big of a performance issue as it was in the 80s and 90s.

OATI is big in that space as well for inter-utility aggregation and transfer, as well as some other company I'm blanking on the name of out of Illinois that was widely used as least in WECC.

Link to America's favorite ISO :)

https://www.ercot.com/gridmktinfo/dashboards