regex - Getting text from inside an HTML tag within a local file with grep

Excerpt From Input File

Municipality: 

JUPITER

My Regular Expression

(?<=)([^]*)

I have an HTML file saved to disk. I would like to use grep to search through the file and output the contents of a specific span, though I don't know if this is a proper use of grep. When I run grep on the file with the expression read from another file (so I dont mess up escaping any special characters), it doesn't output anything. I have tested the expression in RegExr and it matches "JUPITER" which is exactly what I want returned. Thank you so much for your help!

Desired Output

JUPITER