Pennsylvania has had four constitutions since declaring its independence from Great Britain in 1776. The first, which was written in 1776, established a unicameral legislature similar to the one that had been used during the colonial government. Eleven counties and the city of Philadelphia each elected 6 representatives, making for a total of 72 Members in the Assembly.
In 1790, a second constitution was adopted. Under this constitution, the General Assembly was divided into two chambers: the House and the Senate. The new constitution did not set an exact number of members for the House; however, it did state that the Senate should be between one-fourth and one-third the size of the House. An amendment to this constitution was made in 1857, which set a limit of 100 Members in the House. Under both the first and second constitutions, from 1776 through 1878, the General Assembly met annually for 1-year sessions.
The third Pennsylvania Constitution was adopted in 1874. This constitution raised the number of members of the House to a minimum of 200, and guaranteed each county at least one representative. Beginning in 1879, the General Assembly met for 2-year sessions. This practice lasted for 40 years, until the passage of joint resolutions by both the House and Senate in 1957 and 1959 which called for each calendar year to be counted as a distinct session. Sessions continue to be counted in this manner.
The fourth Pennsylvania Constitution was adopted in 1968, and created 203 distinct legislative districts in the state, each with one representative. Pennsylvania continues to have 203 districts/members today.