I have the following SQL

SELECT
    Seq.UserSessionSequenceID, 
    Usr.SessionGuid, 
    Usr.UserSessionID,
    Usr.SiteID, 
    Seq.Timestamp, 
    Seq.UrlTitle, 
    Seq.Url
FROM
    tblUserSession Usr
INNER JOIN  
    tblUserSessionSequence Seq ON Usr.UserSessionID = Seq.UserSessionID
WHERE     
    (Usr.Timestamp > DATEADD(mi, -45, GETDATE())) AND (Usr.SiteID = 15)
ORDER BY Usr.Timestamp DESC

Pretty simple stuff. There are by nature multiple UserSessionIDs rows in tblUserSessionSequence. I ONLY want to return the latest (top 1) row with unique UserSessionID. How do I do that?