User blog comment:Chugite/so are Quality Comics characters public domain or what?/@comment-1212133-20110201221042

Yes Skybandit is correct specifically Blackhawk issues 39-104 were renewed by Arnold and then DC but issues 9-38 were not. However since Blackhawk's first appearance was not renewed the characters are free to use. Plastic Man was renewed from issue 29 -64. http://cocatalog.loc.gov/cgi-bin/Pwebrecon.cgi?ti=1,0&Search_Arg=Blackhawk&Search_Code=TALL&CNT=25&REC=0&RD=0&RC=0&PID=btmXdnYJwd2KWj7LbTv9ktauo&SEQ=20110201165432&SID=1 and http://cocatalog.loc.gov/cgi-bin/Pwebrecon.cgi?PostSearchSortBy1=PUB_DATE&HID=2483550&HID=2494364&HID=2374250&HID=1607062&HID=2494370&HID=2483556&HID=2374256&HID=1607068&HID=2494361&HID=2483547&HID=2374247&HID=1607059&HID=2494371&HID=2483557&HID=2374257&HID=1607069&HID=2483549&HID=2494363&HID=2374249&HID=1607061&HID=2483529&HID=2494343&HID=2374229&HID=1607040&HID=2494357&PostSearchSortBy2=NULL&Search_Arg=Plastic+Man&Search_Code=TALL&ti=1%2C0&CNT=25&PID=ouUm0EOsLsx3RrQKEZ5mgl7YG&SEQ=20110201170334&REC=0&RD=0&RC=0&MAILADDY=&EMAILADDRESS=None&LIMITBUTTON=0