Army Camp at Town Hall 7: 4 of them, max level 6. At Town Hall 18 the cap is level 14. Max level per Town Hall, with how many you can build in brackets: TH3 3 (2), TH4 4 (2), TH5 5 (3), TH6 6 (3), TH7 6 (4), TH8 6 (4), TH9 7 (4), TH10 8 (4), TH11 9 (4), TH12 10 (4), TH13 11 (4), TH14 11 (4), TH15 12 (4), TH16 12 (4), TH17 13 (4), TH18 14 (4).
Tap a Town Hall to open this item there. Dashed: not available at that Town Hall yet.