Is this a Water Line?
Appears to be a water valve with a hose bib connection.  Did you try to open the valve?  I would first locate the house main water shut off valve before you attempt to open the valve just in case the valve fails and floods you kitchen.
Try opening the valve and see if water comes out.  If it does, then I would shut off the house main water valve and replace this old valve with a new one.
Lowes or Home Depot sells the ice maker hookup kits that will connect to this type of water gate valve with the hose bib connector.