In the early 19th century numerous lighthouses were built and reconstructed. However, seafarers kept complaining about the scarcity and poor light quality of the aids to navigation in Russian waters. The situation did not change until the end of the Crimean War in 1856. After that marking of waterways became more effective.

The lighthouse of Keri underwent substantial renovation: in 1858 a metal lighthouse prefabricated in Petersburg was mounted there with a dioptric system commissioned from Paris. A year earlier a metal lighthouse – the first one of its kind in our waters – was put up on Viirelaid islet (Paternoster). In following years a number of cast iron lighthouses was built: in 1864 Vormsi Saksby, in 1865 Kihnu, in 1866 Virtsu (the only cast iron lighthouse destroyed in World War I), in 1871 Vaindloo, 1874 Ristna (in 1920 it was covered with a concrete casing, in 1875 Tahkuna – the tallest metal lighthouse on our coast.

At the end of the 19th century were also built three big stone lighthouses: in 1871, after 20 years of construction, was completed the lighthouse of Mohni to replace the former wooden tower; in 1889 the new Pakri lighthouse was built 80 metres from the old tower put up in 1808, and the Tallinn Southern lighthouse replacing the wooden tower built in 1835.

By the beginning of the 20th century there were approximately 50 lighthouses and harbour lights in Estonian waters. Several wooden aids were replaced by stone and iron towers. In 1907 a beautiful red-brick lighthouse with outbuildings was completed at Laidunina, Saaremaa. Yet, the tower soon lost its importance and as early as at the beginning of World War I its light equipment was transferred to the wooden tower of Kübassaare the light of which was seen to a longer distance in the Gulf of Riga.

A revolutionary change in the light system of lighthouses came after the year 1823 when French physicist Augustin Fresnel invented dioptric light equipment (lens equipment). In the territory of Estonia as well as in Russian empire lens equipment was first introduced in the lighthouse of Keri in 1858. In 1902, incandescent mantle lights hõõgsukklampe replaced the former oil lanterns. However, this method of lighting was labour-consuming and needed constant maintenance and guarding.
In search for reduction of staff and transfer to automated lighting, experiments were made with application of kerosene, petrol and coal gas lanterns. Acetylene gas and the automatic regulation system of flashing light developed by the Swedish engineer Gustaf Dalen, became widely used after the system was improved in the year 1905 and the following years.