Patna Museum has artefacts from of post-1764 period, Bihar Museum focuses from ancient India era to 1764

In a paper entitled "Provincial Pasts and National Histories: Territorial self-fashioning in twentieth-century Bihar" authored by Aryendra Chakravartty, an Associate Professor of History, Stephen F. Austin State University, University in Texas observes that institutions such as the Bihar and Orissa Research Society established in 1915 and the Patna Museum established in 1917 helped the new political-cultural configuration of the region. The former was set up on the lines of ‘Oriental’ institute—the Asiatic Society of Bengal which was established in 1794. The latter was established to house the "archaeological wealth" which were being discovered in Bihar. Sachchidananda Sinha had put forward the proposal for a museum in Patna at the meeting in January 1915 which was convened for the establishment of Bihar and Orissa Research Society. In 1916, the early collection of exhibits for the museum was first housed at the Commissioner’s Bungalow. Edward Gait established the Patna Museum in April 1917. The artefacts were moved to the North Wing of the Patna High Court, which remained a storehouse of artefacts. It was opened to the public in June 1921. The Patna Museum remained attached to the Patna High Court till 1929.

Given the fact that the North Wing of the Patna High Court was inadequate, an initiative to set up a new museum building was taken up in 1925. Bishun Swarup, the chief engineer of the Public Works Department, and Sohan Lal and Brij Narayan were assigned the task of designing an appropriate building. The final plans were approved in December 1926. It emerged as an Indo-Saracenic or Mogul-Rajput-style building. The museum building became fully functional only in 1929 after the current Patna Museum building was inaugurated. 

Chakravartty's paper published in Modern Asian Studies, Cambridge University Press reveals that accidental finding of the Didarganj Yakshi happened at the bank of Ganga by Maulavi Qazi Saiyid Muhammad Azimul on 18 October 1917. It began to be worshiped ‘under the mistaken notion that the figure was a Hindu deity’. It was due to the intervention of J. N. Samaddar, a member of the Society and professor at Patna College, that the statue was removed from the sanctified domain of religion to that of history and archaeology. It was Samaddar who brought the discovery of the statue to the attention of E. H. C. Walsh, vice-president of the Bihar and Orissa Research Society and president of the Patna Museum Committee. It was brought to the Patna Museum. A Didarganj Yakshi statue was the museum's most prized collection, which has been  shifted to Bihar Museum. The artefacts from ancient India era to 1764 are being kept in Bihar Museum and those of post-1764 period are kept at Patna Museum. 

PMC states that "Rahul sankrityayan donated 10000 manuscript which are written in Gold and silver on handmade papers and book on Buddhist philosophy that were once in the library of ancient Nalanda and Vikramshila university. These manuscript were taken to Tibet dating back of around 700 years ago before the destruction of these universities.These manuscripts were brought by him." 

According to Patna Municipal Corporation, "Patna Museum is the state museum of the Indian state of Bihar. Started on 3 April 1917 during the British Raj to house the historical artefacts found in the vicinity of Patna, it is in the style of Mughal and Rajput architecture and is known locally as the Jadu Ghar. Most of the early collections have now been transferred to Bihar Museum."

PMC states that "Items on display in the multipurpose museum include archaeological objects, coins, art objects, paintings, instruments, textiles, paintings, thankas, bronze images and sculptures and terra cotta images by Hindu and Buddhist artists.It has a rare collection of British-period paintings depicting day-to-day life, as well as a fine collection related to the first President of India, Rajendra Prasad. It also houses a World War I cannon. The fossil of a tree said to be more than 200 million years old is on display, as is a casket — unearthed in 1958 by archaeologist, A. S. Altekar, at the Relic Stupa of Vaishali — said to contain the sacred ashes (relics) of Gautama Buddha." It discloses that a project was started in November 2009 to build a replacement museum in Patna to enable the display of larger collections. The decision to construct this world class museum was approved on 26.11.2009 and that was followed by selection of consultant for preparation of a master plan by issuing
advertisement in April, 2010. The work of consultancy and preparation of master plan was awarded to M/s Lord Cultural Resources, Toronto, Canada) through a letter of award dated 31.05.2011. The amount of Rs.4,30,00,000/- quoted by the agency as the ‘total contract fee’ was accepted.M/s Lords Cultural
Resources (LCR) was appointed as consultant for preparing master plan and its allied components was awarded the contracts worth Rs.22,17,20,733/- and was paid a sum of Rs.14,85,28,816.

Now there is a proposal to join Patna Museum and Bihar Museum through an underground tunnel. The Delhi Metro Rail Corporation (DMRC) has released a tender for the construction of underground tunnel between the Bihar Museum and the Patna Museum. The tender was released on February 23, 2023, and bids will be accepted until April 5, 2023. The underground tunnel will be 1.47 kilometres long and will connect the two museums, allowing visitors to easily move between them. The tunnel will be built using the latest technology and will ensure a safe and comfortable journey for the visitors. DMRC has been GIVEN the responsibility of executing this project by Urban Development & Housing Department (UDHD), Government of Bihar. The project is expected to be completed within a period of three years. An MOU has already been signed between UDHD, Govt. of Bihar and Delhi Metro Rail Corporation Ltd. (DMRC) for the underground tunnel between both the museums. It has been claimed that the walls of the tunnel will exhibit art, culture and heritage of the state.

Prior to this, in a case related to Bihar Museum, a division bench of Chief Justice L. Narasimha Reddy and Justice Sudhir Singh of Patna High Court has observed that "we cannot remain oblivious to the gross illegality on the part of the State, not only taking up the project by wasting limited public resources, but also in awarding the contract in a manner which is far from transparent. We, therefore, dispose of the writ petition holding that the project of construction of world class museum in Patna at the cost of about Rs. Five hundred crores in a prime land of 17 ½ acres between the Secretariat and the Patna High Court is not at all in public interest and that the manner in which the contracts of consultancy etc. were awarded is far from transparent and objective. However, we are not intending to stall the project which is nearing
completion. We direct that in case the museum becomes unviable, the building and other infrastructure shall not be alienated to private firms, but shall be utilized for public institutions or purposes."