How do I get the TextBlock in my status bar below to align to the right?

I've told it to:

• HorizontalAlignment="Right"
• TextAlignment="Right"

but the text is still sitting unobediently on the left. What else do I have to say?

<Window x:Class="TestEvents124.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300"
        MaxWidth="700" Width="700"
        >
    <DockPanel HorizontalAlignment="Stretch" Margin="0,0,0,0" Width="Auto">

        <StatusBar Width="Auto" Height="25" Background="#888" DockPanel.Dock="Bottom" HorizontalAlignment="Stretch">
            <TextBlock 
                Width="Auto" 
                Height="Auto" 
                Foreground="#fff" 
                Text="This is the footer." 
                HorizontalAlignment="Right"
                TextAlignment="Right"
                />
        </StatusBar>

        <GroupBox DockPanel.Dock="Top" Height="Auto" Header="Main Content">
            <WrapPanel Width="Auto" Height="Auto">
                <TextBlock Width="Auto" Height="Auto" TextWrapping="Wrap" Padding="10">
                This is an example of the content, it will be swapped out here.
                </TextBlock>
            </WrapPanel>
        </GroupBox>

    </DockPanel>

</Window>