C# - Maintain Generic List Between Postbacks?

Here is what is in my code-behind:

List<Event> events = new List<Event>();
protected void Page_Load(object sender, EventArgs e)
{
}
protected void AddEvent_Click(object sender, EventArgs e)
{
Event ev = new Event();
ev.Name = txtName.Text;
events.Add(ev);
}

I want to add an item to the list every time the Add button is clicked, but the list is reset after every postback. How can I keep the data in the list between postbacks?