Try this instead:
var data = google.visualization.DataTable();
data.addColumn('date', 'Date');
data.addColumn('string', 'State');
data.addColumn('number', 'Unemployment');
data.addRows([
[new Date(2008, 1, 1), "US-AK", 120000],
[new Date(2008, 2, 1), "US-AK", 130000],
[new Date(2008, 3, 1), "US-AK", 140000],
[new Date(2008, 4, 1), "US-AK", 150000],
[new Date(2008, 5, 1), "US-AK", 160000],
[new Date(2008, 6, 1), "US-AK", 170000],
[new Date(2008, 7, 1), "US-AK", 180000],
[new Date(2008, 8, 1), "US-AK", 190000]
]);