Ganesh Chaturthi also known as 'Vinayaka Chaturthi' is celebrated to mark the birth of Lord Ganesha. Historical evidence is available that suggests Ganeshotsav was started by Chatrapati Shivaji Maharaj (1630 to 1680) as a social and public festival.
This was taken forward by the Peshwas of Pune, Lord Ganesha being their family deity (Kul Daivat).
During the British Raj this Hindu festival had largely become a private or family tradition. This was brought to public celebrations as Sarvajanik Ganeshotsav' by Bal Gangadhar Tilak in the year 1893. Bal Gangadhar Tilak intended to unite the Indians and 'Sarvajanik Ganeshotsav' to celebrate Lord Ganesha was the apt platform as Lord Ganesha was loved and worshiped by one and all irrespective of caste and religious lines.
The thought of uniting people through Sarvajanik Ganeshotsav continues even after 126 years and continues to move people to celebrate the Hindu festival for their beloved deity and remover of obstacles fondly called 'Vighna Harta'.
With Mushak (mouse) as his Vahan (vehicle), Lord Ganesha is known by 108 names. Hindus pray to Lord Ganesha before beginning any big or small task as
Vakratunda Mahakaaya
Suryakoti Samaprabha
Nirvighnam Kuru Mey Deva
Sarva Kaaryeshu Sarvada
This means,
The Lord with Curved Trunk, with brightness of a million Suns, I pray to thee to remove all obstacles from the good deeds I plan to perform...