And Missouri, making 18.
The above was in the Texas v. Pennsylvania - Amicu Brief of Missouri et al.
https://www.supremecourt.gov/DocketPDF/22/22O155/163215/20201209144840609_2020-12-09%20-%20Texas%20v.%20Pennsylvania%20-%20Amicus%20Brief%20of%20Missouri%20et%20al.%20-%20Final%20with%20Tables.pdf
are all these states officially in the suit with TX or just have said they will?