As a good student, he obtained a stipend from the Archbishop of Mogilev to study at the Saint Petersburg Roman Catholic Theological Academy.

Therefore, he declined the final ordination to priesthood and attended University of Warsaw for a year to get a teaching diploma.

4 September] 1850[1] to a well-off family of Lithuanian farmers in Girėnai [lt] located near the Russia–Prussia border between Vištytis and Kybartai.

In the aftermath of the Uprising of 1863, the school was undergoing reorganization – it was transformed into a seven-year gymnasium and teaching language switched from Polish to Russian in 1866–1867.

He wanted to continue his studies at the Saint Petersburg Roman Catholic Theological Academy, but the seminary would not grant him a stipend.

In Saint Petersburg, he met Silvestras Gimžauskas [lt] and Kazimieras Jaunius who were also active in the Lithuanian National Revival.

[2] At the time, several noted linguists and philologists, including Lucian Müller, Franz Anton Schiefner, Daniel Chwolson, and Nikolai Petrovich Nekrasov [ru], taught at the academy.

[4] In 1880, Kriaučiūnas completed his exams and received a candidate degree in theology, but as a stipend recipient he would have been obligated to work in the Archdiocese of Mogilev.

He taught Lithuanian grammar that was based on an eclectic mix of previous works by August Schleicher, Friedrich Kurschat, Antanas Baranauskas, Kazimieras Jaunius.

Kriaučiūnas became a strong supporter of Aušra, the first Lithuanian-language periodical aimed at Lithuanians in the Russian Empire – he edited articles, donated funds, distributed physical copies.

A position somewhere in the interior of Russia would have been more prestigious and lucrative, but Kriaučiūnas wanted to remain in his native Suvalkija.

[6] Kriaučiūnas was disliked by Tsarist officials and local landowners and was dismissed from his court job in 1899 and returned to Marijampolė where he started a private attorney practice.

[6] His home was frequently visited by various activists and researchers, including foreigners Jan Niecisław Baudouin de Courtenay, J. J. Mikkola and his wife Maila Talvio, Aukusti Niemi [fi], Eduards Volters, Alexander Alexandrov [ru], Åge Meyer Benedictsen.

[2] His Lithuanian visitors included Antanas Baranauskas, Jonas Jablonskis, Petras Avižonis, Juozas Tumas-Vaižgantas, Gabrielė Petkevičaitė-Bitė, Povilas Višinskis.

[2] He knew eight languages (Lithuanian, Polish, Russian, Latin, Greek, Latvian, German, and French) and had a rich philological library.

[1] He collected examples of Lithuanian folklore (about 160 songs collected by him are known),[6] contributed material to the dictionary of Antanas Juška, translated ten poems from various languages (works by Gavrila Derzhavin, Victor Hugo, Mikhail Lermontov, Friedrich Schiller, Alexander Pushkin, Maria Konopnicka), and wrote a couple papers and articles on language matters.

[6] At the outbreak of World War I, Kriaučiūnas retreated to Vilnius where he lived at the premises of the Lithuanian Scientific Society.