Was Franklin Pierce a liberal president?

Labeling historic figures liberal or conservative is inherently difficult without defining what the terms meant in the times in which the person lived. By today's political standards, yesterday's liberal is today's conservative and vice versa! Let's look at Franklin Pierce through the lens of the 1850s. Pierce is not a well-known president but was in office during an exciting time in American history.
By the 1850s, while the Compromise of 1850 had not wholly settled the question of slavery, it had effectively resulted in a temporary truce between pro and anti-slavery forces. Pierce was a pragmatic New Englander who had won the election over a fellow northerner who had a more aggressive attitude regarding abolition making him unpalatable to southern voters.
Once in office, Pierce promoted expansion west, favorable relations with other foreign powers, and a general message of economic prosperity—all benign political—or so it seemed, for his time in office. Pierce's implementation of expansion is where controversy erupted, and the slavery issue vaulted back into the public consciousness reigniting the animosity between pro and anti-slavery groups. Pierce advocated for Great Britain to give up its interest on the Central American coast. He opened negotiations to purchase Cuba from Spain. Both these seemed to northerners as veiled attempts to pacify southerners who wanted to expand slavery into new territories.
These transactions on their face do not particularly seem a like catalyst for protests. However, flamed by the oratorical and legislative handiwork of Stephen Douglas who was able to convince the Senate to repeal the Missouri Compromise and replace it with the Kansas-Nebraska Act, the question of slavery in the west was reopened with a renewed sense of vigor from both sides of the issue. Douglas used the expansion of the railroad as the conduit for the repeal. Even in the 1850s, infrastructure projects and economic development has bi-partisan appeal even if there are unintended consequences! The unintended result was the violent outbreaks as pro and anti-slave southerners and northerners hastily made for Kansas to determine the future of Kansas. The term "Bleeding Kansas" as it became known was the sensationalized publication of the battles between the ideologies. Some historians believe the Civil War started then, not in 1861.
Peace was eventually restored, and Pierce served out his the remaining of his time with few accomplishments. He would not be renominated by his party for another term. Instead, they chose James Buchanan. Buchanan was considered less favorable to the temptation of pacifying southern interests. Given the priority of western expansion by most of the significant political figures of the day and their priority in establishing the United States as a global power as the main thrust of the 1850s, by historical standards, Pierce was consistent with other leaders in his time in his thinking and promotion of American ideals. By that standard, he would fall more in the conservative than liberal camp.
https://www.history.com/topics/us-presidents/franklin-pierce

https://www.loc.gov/collections/franklin-pierce-papers/about-this-collection/

https://www.whitehouse.gov/about-the-white-house/presidents/franklin-pierce/