The village of Ostrets of the Troyan Municipality became a district of Apriltsi on May 20, 1976. As a settlement it is known since the ancient times. On the Ostrets hill the Thracians have erected a fortress (1055 meters high) and had used it as a hiding place in case of enemy attacks. The fortress named Kaleto has guarded the road through the Rusaliyski Pass to the South Bulgaria.
During the excavations of the fortress in 1953 ceramic artefacts and various weapons are discovered. The artefacts can be seen in the museum in the village of Kravenik.
During the Roman Age on the ridge of the Balkan Range another fortress has been erected named Gradnishka fortress. It served for guarding the road to the town of Philipopolis (town of Plovdiv). Remains of the cobblestone pavement can be seen in the Tazha locality. During the Ottoman rule the fortress was not used and was destroyed. 
Initially the village consisted of nine houses located at the foot of the Ostrets Peak. According to the legend, Princess Mara has passed through the village, the sister of Tsar Ivan Shishman on her way to Istanbul to marry the Turkish Sultan Murad. The peak is called after her, Maragidik. After this event boyars from the town of Tarnovo moved to live in the village and established small villages named Barbulite, Balavurite, Yonovtsi, Kantari, etc. existing nowadays.
The first legal document recognizes Ostrets as a village is dated 1430. The first school is built in 1870. In 1892 the village counted a population of 1534 souls with its own church and municipality building.
In 1876, in the April Uprising, the people from the village of Ostrets took an active part in the battles in both localities – Novo selo and Gradnishka and suffered heavy losses. 
After the April Uprising the village slowly came back to life again and started to develop crafts like woodwork, iron-smithery, fruit-growing and stock-breeding as well. A lot of small stores and pubs were set up.
Nowadays the Ostrets District develops as a touristic destination. The district is surrounded with the Severen Dzhendem Reserve and the peaks of Triglav, Botev, Maragidik and Ostrets as well. The nature determines breezy nights in summer and warm winter. Guests can enjoy many activities as fishing, mountaineering, biking, horse riding, charming places for picnics and beach breaks along the Ostreshka riverside. Attractions include also touristic tours, museums and natural displays that are fun for vacationers of all ages. 
Come and see the magnificent beauty of the nature surrounding the town of Apriltsi!