"PL360 (or PL/360) is a system programming language designed by Niklaus Wirth and written by Wirth, Joseph W. Wells Jr., and Edwin Satterthwaite Jr. for the IBM System/360 computer at Stanford University. A description of PL360 was published in early 1968, although the implementation was probably completed before Wirth left Stanford in 1967."
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PL/360 https://en.wikipedia.org/wiki/PL360
"PL360 (or PL/360) is a system programming language designed by Niklaus Wirth and written by Wirth, Joseph W. Wells Jr., and Edwin Satterthwaite Jr. for the IBM System/360 computer at Stanford University. A description of PL360 was published in early 1968, although the implementation was probably completed before Wirth left Stanford in 1967."
UPL, the systems programming language for the Burroughs B1700/B1800 series of computers.
https://bitsavers.computerhistory.org/pdf/burroughs/SmallSys...
That's a good one. Along the same lines, SYMPL and CYBIL, the systems programming languages for the CDC Mainframe line. Lots of languages like that.