The land of 5-rivers, population-wise the largest, and once known as the granary of east, the Punjab is the lifeline of Pakistan.
To the north of the Punjab is the NWFP (North West Frontier Province) and the Federal capital area of Islamabad. To the north east is the Azad Kashmir. To its east and south is India (Indian Punjab & Rajesthan). To the south west is the province of Sind. To the west is Baluchistan Province and the Federally Administered Tribal Areas (FATA). 
The province is predominantly on level plain. There are, however, some mountainous and hilly areas in the northwest and extreme southwest. There is also a plateau adjacent to the mountains known as the Potohar plateau and a desert belt in the south eastern part known as Cholistan. All the major rivers of the country namely Indus, Jhelum, Chanab, Ravi, & Sutlaj flow through this province. They originate from the Himalayas and pass from north west to south west. They are primeval in nature and the volume of water increases in summer after monsoon rains, resulting sometimes in floods.
Punjab is the most populous province of Pakistan. According to 1998 census, the population of the Province is 7,25,85,000. The population density is 353 persons per square kilometer as compared to the national figure of 164. It contains several major cities of the country: Lahore, Faisalabad, Rawalpindi, Multan and Gujranwala.
In religion, the province is almost entirely Muslim, with a small Christian minority. Punjabi is the mother tongue of 90 percent of the population. The main language used in writing is Urdu, followed by English. The major ethnic groups are the Jat, Rajput, Arain, Gujar and Awan.
The Province of Punjab comprises eight Administrative Divisions and 34 districts. It extends over an area of 2,05,345 square kilometers (97,192 square miles) which is 25.8 percent of the total area of Pakistan.
Ancient History
It was formerly thought that the original inhabitants of the Indus Valley area were the present populations of South India who were displaced by Aryans invaders from the North West, however, recently the Aryan invasion theory has been largely discarded by most scholars. It is now generally accepted that the area of the Indus Valley Civilization has been continuously inhabited for thousands of years by the same general population stock as is presently found in the area of Punjab. The main site of the Indus Valley Civilization in Punjab was the city of Harrapa. The Indus Valley Civilization spanned much of what is today Pakistan and eventually evolved into Indo-Aryan civilization. The arrival of the Indo-Aryan led to the flourishing of the Vedic Civilization that extended from the ancient Sarasvati River to the Ganges river to the entire Indian Subcontinent around 1500 BCE. This civilization shaped subsequent cultures in South Asia. Due to its location, the Punjab region came under constant attack and influence from the west. Invaded by the Persians, Greeks , Kushans, Turks and Afghans, Punjab developed a unique culture that combined that of significant Persian and Central Asian influences, most notable today the influences of Islam.
The city of Taxila, reputed to house the oldest university in the world, Takshashila University, was established by the great Vedic thinker and politician Chanakya. Taxila was a great center of learning and intellectual discussion during the Hindu Maurya Empire. It is a UN World Heritage site, and revered for its archaeological and religious history.
The arrival of Islam
The Punjabis were predominantly Hindu with large minorities of Buddhists like the rest of South Asia, when Umayyad Muslim Arab army led by Muhammad bin Qasim conquered Punjab and Sind in 713. The predominant population of Punjab, and the rest of Pakistan, converted to Islam but there were significant non-Muslim populations including Hindus and later Sikhs. During the reign of Mahmud of Ghazni, the province became an important centre and Lahore was made into a second capital of the Ghaznavid Empire.
The Mughals
The Mughals took control of the region from 1524 until 1739 and would also lavish the province with building projects such as the Shalimar Gardens and the Badshahi Mosque. The Muslim technocrats, bureaucrats, soldiers, traders, scientists, architects, teachers, theologians and Sufis flocked from the rest of the Muslim world to Islamic Sultanate in South Asia and many settled in the Punjab. Following the decline of the Mughals, Nadir Shah sacked the province in 1739 and then the Afghan conqueror Ahmad Shah Durrani annexed the province into his Durrani Empire from 1747 until 1762.
The Sikhs
During the Mughal period, the religion of Sikhism was born and emerged as a formidable military force. After fighting Ahmad Shah Durrani, the Sikhs wrested control from his descendants and ruled in a confederacy, which later became the Sikh Kingdom of the Punjab under Ranjit Singh. A denizen of the city of Gujranwala, the capital of Ranjit Singh's kingdom was Lahore. The Sikhs made many architectural contributions to the city and the Lahore Fort.
The British
The Maharaja's death in the summer of 1839 bought political chaos and the subsequent battles of succession and the bloody infighting between the factions at court weakened the state. Relationships with neighbouring British territories then broke down, starting the First Anglo-Sikh War; this led to a British official being resident in Lahore and the annexation of territory south of the Beas to the British crown.
Post-independence
In 1947 the Punjab province of British India was divided along religious lines as the western Punjabis voted to join the new state of Pakistan while the easterners joined India. This led to massive rioting as both sides committed atrocities against fleeing refugees. The province has rapidly industrialized and is the breadbasket of the country as well as home to the largest ethnic group in Pakistan, the Punjabis.
The undivided Punjab of which Punjab (Pakistan) forms a major region today was home to a large indigenous population of Punjabi Hindus and Sikhs unto 1947 apart from the Muslim majority. According to the 1921 census, the communal ratio of population was Muslims 55.33 per cent and balance 44.67 percent non-Muslims including Hindu and Sikhs.
At the time of Partition in 1947 and due to the ensuing horrendous exchange of populations, the Punjabi Hindus and Sikhs migrated to India. Punjabi Muslims were uprooted similarly from their homes in East Punjab which now forms part of India.
The West Punjabi Hindu and Sikh refugees who moved to India leaving their ancient home lands in Punjab (Pakistan) belonged to various sub groups, clans, tribes, castes and linguistic groups. This includes Khatris, Aroras, Rajputs, Jats, Gujjars, Kambojs, Mohyals, Mazhabis, as well as others such as the linguistically distinct Multanis. A unique feature among Punjabis of different faiths Muslim, Hindu and Sikh hailing from the area which now forms the Punjab (Pakistan) is the enduring affinities to sub grouping and clans cutting across religious lines. Consequently the Muslim Punjabis of Pakistan continue to share common surname with Hindu and Sikh Punjabis of India and Indian Punjab. This includes surnames such as Sahgal, Sial, Bhatti, Ghumman, Sandhu, Tiwana and Cheema.
