Article: Census-wise, the state is placed 21st on the population chart, followed by Tripura at 22nd place. Kangra district was top ranked with a population strength of 1,507,223 (21.98%), Mandi district 999,518 (14.58%), Shimla district 813,384 (11.86%), Solan district 576,670 (8.41%), Sirmaur district 530,164 (7.73%), Una district 521,057 (7.60%), Chamba district 518,844 (7.57%), Hamirpur district 454,293 (6.63%), Kullu district 437,474 (6.38%), Bilaspur district 382,056 (5.57%), Kinnaur district 84,298 (1.23%) and Lahaul Spiti 31,528 (0.46%).

Now answer this question: Who was last in population strength?
Lahaul Spiti